Press Releases

The role of unshared songs in singing interactions between neighbouring song sparrows

sduncan — 2005-09-19T23:25:26Z

We examine how song sparrows use their long-distance songs to modulate territorial interactions. Like most species of songbirds, song sparrows have multiple song types, and because they learn their songs from their neighbors in their first year, a bird will typically share some, but not all, of his song types with any particular territorial neighbor. A song sparrow addresses his neighbor from a distance by singing a song he shares with that neighbor. The neighbour can then escalate the interaction by replying with the same song type (‘type matching’), maintain the interaction at the same level by replying with another but different song they share (‘repertoire matching’), or de-escalate the interaction by replying with a song they do not share.

Note: This research was described in Science News, 18/25 December 2004 (“Song fights: When male birds go tune to tune”, Vol 166, pp 397-399).

The evolution of herbal medicine: behavioural perspectives

sduncan — 2005-09-20T14:32:06Z

The popularity of herbal supplements, and evidence of scientific legitimacy in the use of some medicinal herbs, prompts a question about whether the origin of herbal medicine was the result of animals and humans learning that specific herbs are effective for preventing or treating
certain maladies, or a result of natural selection to seek out and use herbs with markers of efficacy such as a bitter taste? Examining the predictions and requirements of the learned and
evolutionary explanations points primarily to an evolutionary model, which accounts for the use
of ineffective as well as toxic medicinal herbs, and that was expanded by learning and social transmission.

Audience Effects on Food Calls in Captive Brown Capuchin Monkeys (Cebus apella)

sduncan — 2005-09-30T18:04:19Z

Brown capuchin monkeys vocalize when they discover tasty food. These calls, however, change as a function of how much food they have and who else is nearby. We tested how
the brown capuchin calls in the presence of a variety of different audiences, such as other females of different ranks, and the whole group. The results of the study indicate that the monkeys not only change how many calls they produce but also the acoustic features of
the call, such as pitch and loudness. This suggests that the monkeys’ calls may be more cognitively sophisticated than previously thought.

Emergence of division of labor in halictine bees: contributions of social interactions and behavioral variance

sdduncan_manager — 2005-10-04T21:20:53Z

A central question in the study of insect societies concerns the emergence of division of labor. Among the different models of division of labor, the threshold model postulates that it can emerge from initial inter-individual differences in propensity to perform a task. However, social interactions among members of the incipient groups are also likely to shape the genesis of division of labor. We compared task performance and social interactions during nest construction in forced associations of solitary or communal halictine bee. Our work suggests that behavioral asymmetry and social interactions, conditions that were likely to be present at the origins of sociality, might have significantly contributed to the emergence of division of labor in early social evolution.

Influence of plumage colouration on prey response: does habitat alter heron crypsis to prey?

sdduncan_manager — 2005-09-30T16:56:10Z

White plumage has been suggested to increase crypsis to aquatic prey for foraging wading birds. Under this hypothesis, a white-plumaged bird would be less easily
detected than a dark-plumaged bird to aquatic prey such as fish and crustaceans. We tested the hypothesis that white-plumaged herons (e.g. snowy egrets) would be more
cryptic than dark-plumaged herons (e.g. little blue heron) to two species of aquatic prey, mosquitofish and crayfish. Through laboratory and field experiments, we demonstrated
that mosquitofish avoided little blue herons whereas crayfish did not respond differently to the presence of snowy egrets or little blue herons. Our results suggest that plumage coloration in herons may influence crypsis to aquatic prey, specifically fish. These results have implications for the foraging behavior of wading birds.

The choice of arboreal escape paths and its consequences for the locomotor behaviour of four species of Anolis lizards

sdduncan_manager — 2005-10-04T21:44:27Z

We studied four species of arboreal lizards that are a classic example of niche-partitioning, in which species with shorter legs occur on narrower branches than species with longer legs. Accounting for branches encountered as well as chosen by anoles during escape locomotion in natural habitat and in standardized laboratory tests revealed remarkably uniform preference of all species for branches with the largest possible diameter, which is in contrast to the interspecific differences in niche. Thus, our results emphasize the need to account for both resources available and for resources used before making conclusions regarding proximate mechanisms of choice in
animals.

Evidence that 3-keto petromyzonol sulfate specifically attracts ovulating female sea lamprey (Petromyzon marinus)

sdduncan_manager — 2005-10-04T22:01:36Z

Research was conducted to clarify the function of a male sea lamprey sex pheromone. Results are the first to show that the male pheromone only attracts ovulating females.
Results are also the first to show that a synthetic copy of the male pheromone functions in a stream, which confirms the identity and makes this study one of the first in vertebrates
to successfully induce behaviors using a synthetic pheromone. These findings expand our knowledge of pheromone communication in vertebrates, and could lead to new ways
to control sea lampreys in the Great Lakes of North America where they are a destructive, invasive species.

A pair choice test to identify female mating pattern in relation to ovulation in long-tailed macaques (Macaca fascicularis)

sdduncan_manager — 2006-08-08T20:21:11Z

To better understand female mating strategies, male influence over females should be limited. We therefore conducted a pair choice test where female long-tailed macaques controlled access to males in order to identify how female behaviour and the ovarian cycle affect choice and number of mates. Six females and four males participated. Twice a day, females were presented with two males and allowed two choices. Females mated with multiple males in all ovarian cycle phases. They apportioned choices and copulations evenly across males and did not prefer dominant males. This contrasts with mating in the wild, where dominant males monopolize copulations.

Dietary Amino Acids Influence Plumage Traits and Immune Responses of Male House Sparrows (Passer Domesticus), but not as Expected

sdduncan_manager — 2005-10-04T22:17:50Z

Many birds have patches of black in their plumage. The size of these patches appears to
function as a signal, yet little is known about how the patch reveals information about the
bearer. One possibility is that melanin, the black substance in the plumage, requires
amino acids that are valuable for other functions, such as immune responses. We tested
this possibility in house sparrows by manipulating the amount of amino acids in their diet
during moult. We found that deficiencies of two amino acids appeared to reduce melanin
synthesis but did not alter its size. The distribution of amino acids also affected antibody
production, but the two involved in melanin synthesis did not. These results suggest that
development of informative signals depends on other processes.

Correlates of territorial boundary patrol behaviour in wild chimpanzees

sdduncan_manager — 2006-02-08T19:23:50Z

Male chimpanzees show a unique form of cooperative territorial defense that includes patrols of
territory boundaries and incursions into neighboring territories, where they may make lethal
attacks on conspecifics. Researchers have studied the functions of territoriality (e.g., defense of
food resources), but have not examined day-to-day decision-making about patrolling. Our
observations at Ngogo, in the Kibale National Park, Uganda, show that the number of males who
associate per day is the best predictor of whether males will patrol on any given day. Males
patrol more often when ripe fruit is abundant, but this is because they form large parties at such
times. The presence of estrous females has no apparent effect on the likelihood of patrolling.
Our data support the hypothesis that the risks associated with intergroup aggression, which
depend on the number of males present, are the main influence on willingness to make
potentially lethal attacks (the “imbalance of power” hypothesis). Because chimpanzees have a
fission-fusion social system, patrols can lead to low-cost opportunities for males to kill members
of neighbouring communities many males patrol together. Males at Ngogo reduce the risk of
patrolling and establish competitive asymmetries in their favour by patrolling in large parties.

Can the alternative male tactics 'fighter' and 'sneaker' be considered 'coercer' and 'co-operator' in coho salmon?

sdduncan_manager — 2005-11-10T16:52:31Z

In many species, there are alternative male types that look and behave differently. For example, some males are large and fight with other males for access to females for mating while other, smaller males apparently sneak matings. It is widely accepted that females of these species prefer to mate with large, fighter males. This paper re-examines that assumption in coho salmon, a species with alternative male types. The findings are that females apparently prefer small, sneaker males who cooperate with females. But females often mate with large males to avoid harassment by them. Who females mate with depends on the costs and benefits of any given situation.

Characterizing the mating behaviours of the Tamesi molly, Poecilia latipunctata: a sailfin with shortfin morphology

sdduncan_manager — 2005-11-10T17:13:25Z

The endangered Tamesi molly (Poecilia latipunctata), an unusual live-bearing fish, shows both sailfin and shortfin molly mating behaviours. Although genetically a sailfin molly, P. latipunctata lacks the enlarged dorsal fin. P. latipunctata males perform courtship displays to females to elicit cooperation similar to sailfin males. However, males also establish dominance hierarchies through agonistic acts and changes in colour like shortfin mollies. We found that both female receptivity and presence of other males influence type and intensity of male mating behaviours.
These context-dependent male mating strategies may have been important in the divergence of P. latipunctata from their sailfin molly ancestors.

Territory revisitation reduces intrusion during spawning trips by female yellowtail damselfish.

sdduncan_manager — 2005-11-10T17:35:17Z

Like humans, non-human animals are faced with difficult decisions about how to manage conflicting demands. For example, when we go to work or leave for vacation, we leave our homes unattended and thus exposed to intrusion. We solve this problem by using locks, guard dogs, alarms or by relying on neighbors. But, what if we these solutions were not available? Female yellowtail damselfishes aggressively defend territories that provide their food and shelter on Caribbean coral reefs but experience intrusion when they leave their territories at dawn to spawn in the territories of males. Spawning can last an hour or more allowing other members of the same species to invade the territory. Some, but not all, females return to their territories at intervals during spawning. We found that when females that returned during spawning were caged during the spawning period to prevent returns, they experienced more intrusion than when they were allowed to return to their territories. Returning reduced intrusion rates to levels similar to those occurring when the fish was continuously present in its territory on non-spawning days. Females that did not return during spawning did not experience an increase of intrusion during caging. Thus, female damselfish appear to resolve the conflict over protecting their territory while they have important business elsewhere by periodically returning home to check on things, but only if intrusion would be likely to increase significantly during a continuous absence.

Dominance rank relationships among wild female African elephants (Loxodonta africana)

sdduncan_manager — 2005-11-10T22:13:42Z

From savanna baboons to spotted hyenas, many female primates and social carnivores form close and enduring social relationships with their female kin. These relatives often help each other in conflicts. As a result, a young female comes to occupy a dominance rank just below her mother, eventually “inheriting” her dominance rank. Here we report that female African elephants—who
also have close and enduring relationships with kin—do not have these same “nepotistic” dominance hierarchies. Instead, rank is based on age and size. Our results suggest that in elephants, close female bonds probably evolved for sharing ecological and behavioral knowledge and skills rather than for within-group competition.

Coccidian oocyst parasitism in the blue-black grassquit: influence on secondary sex ornaments and body condition

sdduncan_manager — 2006-02-08T19:25:21Z

Female birds choose males that exhibit exuberant morphological characteristics and/or behavior, which may decrease survival of these males. Different hypotheses suggest that parasite-resistant males should have brighter plumage and more energetic behavioral displays, or should be in better physical condition than parasitised males. To test these hypotheses we evaluated behavioural and mophological characteristics of neotropical blue-black grassquits, and sampled their intestinal parasites. We found that heavily parasitised males have shorter display leaps and more patchy plumage when compared
with less parasitised males. However, we did not find that males in better condition exhibit brigher plumage or display more energetically.

The nature and representation of individual recognition odours in Belding’s ground squirrels

sdduncan_manager — 2006-02-08T19:21:25Z

Individually distinct cues are useful when animals interact repeatedly over time and when discrimination among multiple familiar individuals is beneficial. To understand how animals recognize each other socially, we need to know the sources and distribution of recognition cues, as well as how others perceive these cues. Here I show that Belding's ground squirrels, a highly social mammal, produce at least five individually distinct odors (from oral, dorsal, pedal and anal glands and from supraorbital areas), and that they incorporate multiple odours into their memories of conspecifics, suggesting a mental representation of familiar individuals. These odors may allow accurate discrimination of conspecifics along several social dimensions.

Development-related effects of an acanthocephalan parasite on pairing success of its intermediate host, Caecidotea intermedius (Isopoda)

sdduncan_manager — 2006-02-08T19:27:01Z

The acanthocephalan parasite, Acanthocephalus dirus, infects both an aquatic crustacean (first host) and a fish (second host) during its life cycle. Previous work has shown that development of the parasite correlates with changes in both the appearance (color) and behavior (activity, hiding) of the first host and that these changes increase conspicuousness to the second host. We examined whether parasite development also correlated with changes in the sexual behavior of the first host (aquatic isopod, Caecidotea intermedius). We compared the sexual behavior of males that differed in infection status (early-stage vs. late-stage parasites present) and found that parasite development correlated with variation in male sexual behavior. Specifically, that males infected with late-stage parasites were less likely to initiate mating attempts with females than males infected with early-stage parasites. We discuss the results in the context of both pathological effects of infection and strategic manipulation by the parasite.

Multiple breeding strategies in the swift fox, Vulpes velox

sdduncan_manager — 2006-02-08T18:57:09Z

Little is known of the mating system of the swift fox (Vulpes velox) or how it compares to other socially monogamous mammals. We used microsatellite analysis in conjunction with spatial observations to investigate swift fox mating strategies. The mating strategies employed by swift foxes were highly diverse. Previous field observations have indicated that the swift fox is socially monogamous. However, we found that extra-pair mating was a common breeding strategy, and there was also variation in the structure of social groups. In addition, swift foxes engaged in mate switching which refutes the prevailing hypothesis that they always mate for life. Thus, we found that the mating system of the swift fox is highly diverse and substantially more complex than previously believed. Factors that may influence which strategies are adopted and whether they are adaptive are discussed.

Alloparental feeding in the king penguin

sdduncan_manager — 2006-03-06T19:26:52Z

The austral ocean imposes severe limits in the accessibility to the food for many seabirds. In that context, breeders must periodically leave their offspring unattended. During parental absenteeism, fasting chick may gain allofeedings, i. e. supplements of food from other breeders than their own parents. We studied allofeeding in a king penguin colony, a seabird
in which parents leave their fasting chick in dense crèches up to several months running. During winter, more than 1/5 of adults allofed almost 2/3 of the chicks. Numerous breeders that have lost their own offspring became allofeeders, although successful breeders occasionally allofed. Chicks were allofed preferentially by adults that were their close neighbours when the colony was still organized into breeder territories. Although allofeeding is commonly associated with an altruistic behaviour, it was not strictly the case in king penguins because allofed chicks increase their survival without cost for the allofeeder.

Development of red-eyed treefrog eggs affects efficiency and choices of egg-foraging wasps

sdduncan_manager — 2006-01-20T19:05:50Z

Foraging theory predicts that predators choosing between prey of equal value will prefer those they are more likely to capture. Eggs are excellent and usually easy prey. However some embryos, such as red-eyed treefrogs, can escape from predators by hatching prematurely when attacked. Warkentin, Buckley and Metcalf asked if wasps foraging on red-eyed treefrog embryos prefer younger eggs that cannot yet hatch. They found that young eggs have a second defence mechanism: a thick jelly coat that becomes thinner as they developed. Wasps had difficulty extracting young embryos from this jelly, and in fact preferred to feed on older, more accessible eggs, even if they could hatch. This reduced the overall number of eggs killed, and shifted most of the mortality to intermediate stages, when eggs were losing their maternally-provided jelly defence, but had not yet developed the ability to escape by hatching. Eggs are not all equal to predators.

Non-random patterns of vigilance in flocks of the greater flamingo (Phoenicopterus ruber ruber)

sdduncan_manager — 2006-02-08T19:07:49Z

Animals gather information about predators when they interrupt feeding activities and raise their heads. Recent studies suggest that feeding activities should be interrupted at regular rather than unpredictable time intervals when foragers are threatened by predators that rely on surprise rather than stealth. Regular scanning has rarely been documented in
relation to predator behaviour. I examined vigilance patterns in greater flamingos foraging in a lagoon complex in Venezuela. Scanning behaviour was more regular than unpredictable in this large species where disturbance by people probably represents the most likely threat and which is therefore best detected using regular scanning.

Wounding, mortality and the lion's mane (Panthera leo)

sdduncan_manager — 2006-02-08T19:10:57Z

A protective role for the lion's mane has long been assumed but this assumption has never been tested. We compared patterns of injury, mane development and adult mane morphology in a population of
African lions and found no compelling evidence that the mane conferred effective protection against wounding. The mane area was not a specific target of attacks, and injuries to the mane area were not
associated with higher mortality than other injuries. Regions of the mane that were most frequently attacked did not show earlier onset of mane growth in subadult males, or longer/darker mane hair in adult males.
Adult males appeared to be wounded less frequently on the mane area than predicted by surface area, but it is unclear whether this trend was only caused by observer bias due to decreased visibility. We conclude
that while the mane may have conferred protection during the early evolution of the trait, protection appears to be secondary to the strong sexually-selected advantages of the mane as a condition-dependent ornament.

Sex differences in rates of territory joining and inheritance in a cooperatively breeding cichlid fish.

sdduncan_manager — 2006-02-08T18:19:12Z

In some species, called “cooperative breeders”, only male and one female in the group breed, while other group members (“helpers”) help them raise their young. Such cooperation and reproductive segregation raises many questions. How does an individual become a breeder in such a system? What do these helpers gain by helping? Stiver et al. investigate these questions by using underwater behavioural observations on a cichlid fish native to Lake Tanganyika, Africa. The researchers removed the breeding male from
some groups and the breeding female from others, and found that female helpers tended to inherit the breeding spot in the group they currently live in, while male breeding vacancies are typically filled by individuals that join the group. Helpers helped more when they were related to the new breeder. This study provides insights into how cooperation may have evolved and how changes in status influence individuals in social groups.

Mind the Gap: Means-End Discrimination by Pigeons

sdduncan_manager — 2006-02-08T19:12:06Z

Four experiments examined how pigeons learned two tasks designed to reveal their
understanding of means-end relations. The purpose of these experiments was to reveal
how different kinds of animals think about the world and how these capacities might have
evolved. The pigeons were required to retrieve out of reach food by selecting among a
ribbon attached to a food dish and one that was not. All of the pigeons came to select the
“connected” ribbon. Further tests designed to investigate how they learned this solution
suggested that it was solved based on the perceptual cues directly related to the ribbon
rather than a deeper conceptual understanding of the ribbon as a “means” to an end
(getting the food). Comparisons with similar results from primates suggest that some
differences between species may exist, but that caution is still needed in interpreting such
results because of procedural differences among the tests.

Site-dependent Aggression and Mating Behaviour in Three Species of Nasonia (Hymenpotera: Pteromalidae)

sdduncan_manager — 2006-03-06T18:58:19Z

We wanted to investigate the relationship between female mate availability and male aggression and area defense using three closely related species of the parasitoid wasp Nasonia. These three species differ in the frequency of females that emerge as virgins, and we wanted to determine if males will defend an area with females that are not virgin. We found that in one species, Nasonia vitripennis, 95% of females emerge as virgins and males are highly aggressive and stay on or near the host from which they emerge. One hundred percent of N. giraulti females emerge having already mated, and males do not defend the area and disperse. Finally, female N. longicornis are highly variable in the frequency of virgin females, but males are still aggressive. We believe this major difference between the species may have been caused by genetic or bacterial factors that limit successful reproduction between all three species.

Asymmetrical incest avoidance in the choice of social and genetic mates

sdduncan_manager — 2006-03-06T19:23:10Z

Even though incest generally results in lower reproductive success, it may occur if animals don’t have enough information about a prospective mate to estimate their relatedness or if the costs of avoiding inbreeding are too high. Over a 17-year period, Savannah sparrows (Passerculus sandwichensis) in an island population rarely paired incestuously (15 of 1609 nesting attempts). Most cases involved 1-year-old males breeding for the first time with aged females. Father- daughter matings (social and genetic) were avoided completely. These results suggest that there are fundamental differences in the likelihood of incestuous matings depending upon sex, age, and specific relationship.

Changing territories, changing tunes: male loons, Gavia immer, change their vocalizations when they change territories

sdduncan_manager — 2006-03-06T19:35:37Z

Male Common Loons produce a territorial vocalization called the "yodel". Each male loon has a characteristic yodel that is stable from year to year and differs from that of other male loons on other lakes. Of 13 male loons whose yodels we recorded before and after male loons changed territories, 12
substantially changed their yodels either the first or second year on the new territory. Further, this change was such that it increased the difference between their yodel and that of the previous resident of the territory. This result implies that loons not only change their vocalizations as the birds change territory but also that the new owner is familiar with the yodel of the resident that it replaces.

Variation in body temperature and the isolation calls of juvenile big brown bats (Eptesicus fuscus): consequences for individual recognition.

sdduncan_manager — 2006-03-06T19:48:15Z

In frogs and insects, communication sounds change as the individual’s body temperature changes. This complicates communication and individual identification. For most mammals, body temperature is constant and communication signals do not vary. However, in mammals that vary their body temperature as a means of saving energy, vocal communication may be compromised. We found that young big brown bats can vocalize even at body temperatures of 11^oC, but calls vary depending on body temperature. This may compromise a mother’s ability to identify her offspring. Maintaining body temperature by clustering, or using cues such as odour, may allow pups and mothers to reunite.

Sexual selection and social rank in bighorn rams.

sdduncan_manager — 2006-03-06T19:57:42Z

In many polygynous species, male reproductive success increases with social rank. Because rank is established through aggressive interactions among males, it should increase with body mass, because larger males should have a competitive advantage during fights. A positive effect of mass on social rank should select for high sexual dimorphism in body mass in ungulates. Because it is difficult to weigh free-ranging ungulates, however, empirical data on the relationship between mass and male social rank are scarce. We monitored individual mass, age and social rank of marked bighorn rams (Ovis canadensis) at Sheep River, Alberta, over 5 years. In this species, access to estrous ewes during the rut in mainly determined by ram social rank. We found that both mass and age were important determinant of social rank but the relative role of mass increased as rams aged. That is because up to about 6 years of age older rams are also inevitably heavier than younger rams. Once males reach their adult body mass, if they are large they can win fights again older conspecific. Our results support the idea that sexual selection may have led to the substantial sexual dimorphism seen in most ungulates.

Risk assessment by grasshopper mice (Onychomys spp.) feeding on neurotoxic prey (Centruroides spp.)

sdduncan_manager — 2006-04-13T21:09:33Z

Grasshopper mice are voracious arthropod predators in NA deserts and grasslands; many of their prey possess noxious defenses, including the sprays of stink beetles and the stings of scorpions. Some reports suggest grasshopper mice modify their attacks to neutralize the specific defenses of their prey (such as targeting a scorpion’s stinger), while other studies show the mice attack indiscriminately. We looked for prey-specific attack behavior using staged encounters with 38 wild-caught mice, testing each mouse with a bark scorpion (a dangerous, neurotoxin-wielding prey), with a stripetail scorpion (a non-neurotoxic prey), and a lab cricket (a defenseless prey). Mice attacked all three indiscriminately, but did have significantly more difficulty subduing bark scorpions. Our results suggest that grasshopper mice use a simple rule when attacking small invertebrates; i.e., if it moves and smells like food, attack! Moreover, our study demonstrates the mice are resistant to the potent neurotoxins of bark scorpions.

The role of testosterone in male downy woodpeckers in winter home range use, mate interactions, and female foraging behaviour

sdduncan_manager — 2006-04-13T21:19:02Z

We captured male downy woodpeckers in winter and inserted under the skin small implants filled with testosterone. We released them the same day and followed the males and their female mates regularly to determine what effect the elevated levels of
testosterone would have on male behavior, and what effect a change in male testosterone level might have on females associating with those males. Comparing our experimental males with normal males without elevated testosterone, we found that testosterone actually decreased the frequency of aggressive male-male encounters, it changed the way a male uses space within its home range (or territory), and it leads in some cases to increased male-female interactions. These interactions seemed to impact the female mates of testosterone-implanted males in several negative ways, including a reduction in
foraging behavior and a reduction in the frequency of a female’s social interactions with non-mate males.

Regulation of Space Use in a Solitary Field: Population Density or Prey Availability?

sdduncan_manager — 2006-04-13T21:34:42Z

Home range size in birds and mammals appears to be influenced by a number of factors including food availability, body mass, and population density. However, few studies have convincingly shown population density to influence the extent of space use in a population of free ranging carnivores without a corresponding increase in food availability. We investigated the relative effects of food availability, body weight, and increased density on the size of adult bobcat (Lynx rufus) home ranges and core areas in Mississippi, USA from 1989-1997. We observed an increase in population density and a decrease in annual mean home range and core area sizes for males and females during this 9-year study. Population density explained 64% and 56% of the variation in home range size for males and females, respectively, whereas food availability and body weight failed to explain the observed reduction in bobcat home range size. Population density was also the most important variable explaining variation in core areas for both sexes, although food availability also appeared to play a role, especially for females. We suggest that population density should be considered along with energy acquisition and metabolic factors such as food availability and body size when investigating variability in home range and core area sizes of mammals.

Polybia wasp biting interactions recruit foragers following experimental worker removals

sdduncan_manager — 2006-04-13T21:45:05Z

Communicative interactions among colony members, or worker connectivity, can affect division of labour in insect societies. In this study I used experimental forager removals to test whether biting interactions among wasp workers is a form of worker connectivity. I asked whether biting induces new recruits to enter the foraging force. I observed colonies with individually marked workers during a pre-treatment (control) period, then removed all arriving foragers on the following day. Foraging ceased in the colonies after several continuous hours of forager removals, and remained depressed on the following morning. I observed the colonies on one to three additional days, and I grouped the remaining workers into four behavioural categories: non-foragers, individuals that stopped foraging after the manipulation, continuing foragers that were active before and after the manipulation, and recruited foragers that began foraging after the manipulation. After the manipulation, the recruited foragers were bitten at similar rates to the continuing foragers. Workers in the other behavioural categories were bitten at lower rates. Most importantly, the recruited foragers were the only behavioural category that were bitten at significantly increased rates after the manipulation. The experiments show that biting plays a role in inducing foraging. Biting is a form of worker connectivity, serving as a mechanism of communication among Polybia workers that affects colony responses to changing conditions.

Line-following preferences of male crab spiders Misumena vatia

sdduncan_manager — 2006-04-18T17:36:07Z

Spiders, including the crab spider Misumena vatia, typically leave silken lines (draglines) behind them as they move. These lines allow spiders to prevent falls, as well as serving in a variety of other possible ways. Females of some species place sex-specific odors (pheromones) on these lines, which may also provide adult males with information that helps them to find virgin adult females. However, female Misumena do not produce odor cues that males can use. Adult males nevertheless respond positively to lines of their females, probably using tactile cues present on the lines. Immature males do not respond preferentially to these lines, which provide them with no advantages – following them would simply increase their vulnerability to the frequently cannibalistic females. Thus, draglines may function in more than one way, which may differ with both sex and age.

Effects of natal experience on habitat selection when individuals make choices in groups: a multilevel analysis

sdduncan_manager — 2006-04-18T17:47:48Z

When animals make choices in groups, an individual's decisions may be affected by the behaviour of other individuals in the same group. In this paper we demonstrate how one can use multilevel statistical models to study habitat preferences when animals make choices in groups, and when individual decisions are affected by the behaviour of other animals who are making choices in the same experiment. In particular, we show that when female Drosophila melanogaster select a new habitat, their habitat preferences are affected by a number of factors, including the type of habitat they experienced prior to making the choice, as well as the choices made by other females during the previous hour in the same trial. A comparison of analyses based on traditional statistical approaches (generalized linear model, GLM) with those based on the multilevel model indicates important discrepancies between the results of the two models, probably because the GLM was unable to include factors affecting choice that were shown to have important effects on choice in the multilevel analysis. This study demonstrates the utility of multilevel statistical models for addressing problems in animal behaviour.

Predator learning, experimental psychology, and novel predictions for mimicry dynamics

sdduncan_manager — 2006-04-18T18:12:21Z

The evolution of warning colouration and defensive mimicry is driven by predator avoidance learning and behaviour. Animal learning data from experimental psychology can further inform our predictions of predator behaviour and improve our conceptualization of predator behaviour and predictions for mimicry dynamics. I consider how relevant findings in animal learning, particularly the importance of contextual cues in mediating behaviour, may provide new insight for the evolutionary and ecological dynamics of defensive mimicry. Specifically, work in animal learning psychology predicts that (1) a Batesian mimic will be less disadvantageous for the model species than previously assumed, (2) contextual cues will be a selective agent in behaviour and/or distribution of model and mimic individuals, and (3) multimodal signals will contribute to model and mimic species context specificity, particularly in species with no opportunity for unique ecological cues. These predictions may help explain ecological/behavioural empirical data currently considered incongruous with mimicry theory
predictions.

Urban bioacoustics: it's not just noise

sdduncan_manager — 2006-04-18T18:26:46Z

The sound environment plays a major role in shaping the ways that animals communicate. Humans, particularly in cities, profoundly alter the sound environment. Humans increase noise levels through automobiles and other machines, and structures built by humans (homes, buildings, highways) alter the ways that sound moves through the environment, creating reflective surfaces and impediments to sound transmission. Several recent articles have identified effects of human-generated noise on animal communication and behaviour. These studies, however, serve to highlight the surprising lack of research on the behavioural responses of animals to altered sound environments. We describe several important characteristics of urban environments, all of which have parallels in natural environments. We suggest that cities are a fruitful area for future research on the evolution of animal communication systems, with implications for conservation in human-altered environments more generally.

Meat sharing among the Gombe chimpanzees: Harassment and reciprocal exchange

sdduncan_manager — 2006-07-06T18:35:23Z

Sharing food with unrelated individuals seems detrimental, yet it occurs in many species, including birds, bats and primates. Meat sharing among wild chimpanzees is a classic example of this phenomenon. I evaluated two explanations for nonkin meat sharing among wild chimpanzees at Gombe National Park, Tanzania. There was strong evidence supporting the idea that these chimpanzees share to avoid the costs imposed by persistent beggars. Meat possessors ate more slowly when faced with many beggars, and were more likely to share with beggars that persistently harassed them. Meat recipients stopped harassing the possessor. In contrast, there was mixed support for the idea that chimpanzees exchange meat for social “favours”. Males did not share preferentially with frequent male grooming partners or sexually receptive females. Possessors were more likely to share with frequent female grooming partners; however this was likely to be due to increased harassment by these females.

Contact call diversity in wild Orange-fronted parakeet pairs (Aratinga canicularis)

sdduncan_manager — 2006-07-06T18:47:20Z

Social animals rely on contact calls-- a type of vocalized sound-- to establish and maintain the connections so important to their life-style. Animals that live in stable social groups often share a common contact call, while animals that live in societies with more fluid structure often show individual distinctiveness. In these animals, such nametags could be used to address and make connections with specific individuals. Both parrots and dolphins live in fluid societies. Dolphins show both individually distinctive (signature) contact calls, and mimicking of other individuals' signatures while socializing. We examined the contact calls of wild Orange-fronted parakeets in Costa Rica, to see if they similarly produced signature contact calls, and if contact calls were shared within mated pairs, the only stable social grouping seen in this species. We found that individuals do produce signature calls, and that mated pairs, while not sharing a common call, do show call similarity.

Leaf-cutter ant species (Hymenoptera: Atta) differ in the types of cues used to differentiate between self and others self and others

sdduncan_manager — 2006-07-06T19:17:58Z

Ants are among the animals living in the most sophisticated societies. Here we search the chemical cues that these insects use when discriminating self from other. Nestmate recognition among most social insects is thought to be mediated by cuticular hydrocarbons. Here we show that among two closely related ant species, the chemical cues used for recognition vary between them and that they are not cuticular hydrocarbons, but chemicals secreted from the mandibular gland that produces their alarm pheromone and possibly another gland in the gaster. We performed experiments with free living colonies of Atta laevigata and Atta cephalotes using live and dead dummies, some impregnated with glandular extracts, allowed us to reconstruct the recognition cues Our results suggest that recognition mechanisms vary among ants, and may thus vary among other social insects, and are shaped by various evolutionary forces in addition to kin selection.

What makes information valuable: signal reliability and environmental uncertainty

sdduncan_manager — 2006-07-08T21:05:19Z

To acquire information, animals can track the likelihood of events, or pay attention to external signals. We developed mathematical predictions and then tested the value of different kinds of information to six captive blue jays (Cyanocitta cristata). The birds repeatedly chose to peck either a red or green key to obtain a food reward. We varied the overall probability that pecking red led to a food reward. A third key acted as a signal, and we varied how reliably this signal indicated the true colour from trial to trial. We found that blue jays used the signal when it reliably indicated the correct behaviour and the environment was uncertain. Blue jays ignored the signal when it indicated the true colour unreliably and when prior experience gave them a high level of certainty about the
true colour. Overall, we observed a bias towards using personally acquired experienc

A dynamic method to study the transmission of social foraging information in flocks using robots

sdduncan_manager — 2006-08-01T14:30:57Z

Robots could be excellent tools to investigate the dynamics of social behaviour in animals, such as, flock formation, social information transmission, etc. We assessed the potential use of robots in social contexts by studying the behavioural reactions of adult house finches (Carpodacus mexicanus) to robot behaviour. We found that the presence and motion of robots elicited responses that were similar to those given to live flock-mates. In general, house finches invested more time to foraging as the robots increased the duration of head-up bouts, which could be associated to the perception of foraging opportunities or to higher levels of flock anti-predator behaviour. We conclude that robots are a novel technique for animal behaviour with broad applications to the study of social behaviour and visual social cognition, because they allow detailed studies of the proximate and ultimate mechanisms underlying behavioural patterns and they have the potential to interact with live individuals.

Forager activation and food availability in harvester ants

sdduncan_manager — 2006-08-01T14:42:38Z

Ant colonies operate without central control, but are able to adjust foraging activity in response to food availability. In the field, we found that foraging activity increases with the return of successful foragers, and is unaffected by the return of unsuccessful foragers. We then compared our field observations to the outcomes of computer simulations. The computer model that best describes the results is one in which an inactive forager immediately joins a queue to leave the nest upon encountering a successful forager. This behaviour allows colony foraging to track food availability without memory or the capacity to monitor colony-level activity.

Montezuma oropendolas modify a component of song constrained by body size during vocal contests

sdduncan_manager — 2006-08-01T14:55:00Z

The sound frequencies of an animal's vocalization can reflect body size; larger
individuals are able to produce lower frequencies than smaller individuals. In some frogs, for example, individuals use these frequencies to assess the size of their opponents. Here we provide evidence for similar behavior in a bird. The Montezuma oropendola is a polygynous songbird in which male size is an important factor in mating success. During interactions at nesting colonies, males appear to lower the frequencies of some parts of their songs, suggesting that they have an important function in advertisement. Comparisons to other bird species indicate that these sounds are produced near the lower limit of what the birds can produce.

Taming of the skew: transactional models fail to predict reproductive partitioning in the paper wasp Polistes dominulus

sdduncan_manager — 2006-08-01T15:07:12Z

Behavioral ecologists have spent much of the past two decades trying to explain why and how cooperative groups can be stable when reproduction within the group is asymmetrically shared. Polistes paper wasps have been at the forefront of this investigation because of their colony-initiating behaviors. When females cooperatively initiate colonies, reproduction is often distributed unequally, and sometimes completely monopolized by one individual. Transactional models of reproductive skew assume a “social contract” where the dominant controls group
membership and may yield some reproduction to a subordinate as an incentive to stay. We tested predictions of these models in P. dominulus. The results were unsupportive. For example, we found no relationship between skew and relatedness, and observed colonies wherein reproduction was completely monopolized by dominants unrelated to subordinates. Overall, our results demonstrate that transactional skew models have little predictive power and are unlikely to yield further insight into Polistes wasp societies.

Reduced territorial responses in dark-eyed juncos, Junco hyemalis, following population establishment in a climatically mild environment

sdduncan_manager — 2006-08-02T15:16:50Z

Male songbirds respond to playbacks of their own species songs by aggressively
approaching the source of the playback. Here we show that male dark-eyed
juncos from different populations have different territorial responses throughout
the course of their breeding seasons. In southern California this species
normally inhabits the higher altitudes of the Sierra and males show very strong
responses to playback. By contrast males in a small population of juncos on the
coast in San Diego show much weaker responses. The San Diego population is
believed to have been founded by a small flock of birds from the Sierras in about
1980. We suggest that the weaker responses in San Diego are a consequence
of the much longer breeding season given the milder climate. The study
highlights how novel environments cause dramatic changes in social behavior.

The Role of Social Context and Individual Experience in Novel Task Acquisition in Cotton-top Tamarins (Saguinus oedipus)

sdduncan_manager — 2006-08-01T16:05:18Z

Many animals use social cues from conspecifics to help determine what to eat or how to find food. However, in many species dominance interactions limit opportunities for
individuals to closely observe and interact with skilled group members. We studied how naïve individuals learn novel foraging behaviour within the cotton-top tamarin, a new world monkey characterized by high levels of social tolerance. We designed a novel foraging task and trained some monkeys to be skilled in the task. We then exposed naïve tamarins to the foraging task either alone, with skilled mates, or with mates who did not know how to solve the task. Tamarins could not readily learn the novel task when they were tested alone, or with other naïve tamarins. However, tamarins could rapidly learn the task when they were tested with skilled mates. Our study shows that in a species with a tolerant social structure, individuals rely primarily on social cues to learn novel tasks.

Ontogeny of locomotory behaviour in the American locust, Schistocerca americana: From marathoner to broad jumper.

sdduncan_manager — 2006-08-01T16:15:20Z

The endurance and power output of running and swimming vertebrates improves with age. Do similar trends exist in invertebrates? American locust grasshoppers (Schistocerca americana) increase in body size by about 200-fold in the 7 seven weeks of development from hatching to adult. To determine if jumping performance varied during development, we forced grasshoppers of different ages (juveniles at 3 different stages and adults) to jump for twenty minutes. We measured their jump frequency, endurance, speed, and power output. Surprisingly, we found that younger grasshoppers had greater endurance, but like juvenile vertebrates, had lower power outputs than adults. The developmental changes in jumping performance match ecological and behavioural observations of foraging, dispersal, and migration, as juveniles only hop but adults can fly.

Intensity of interference affects the distribution of house sparrows Passer domesticus at food patches

sdduncan_manager — 2006-08-02T20:26:53Z

The Interference Ideal Free Distribution (IFD) model predicts that foragers should settle
in patches of high resource abundance when aggression/interference among competitors
is weak but should spread out evenly across patches when aggression/interference is
strong. We tested this prediction by observing house sparrows (Passer domesticus) at a
rich and a poor patch differing in seed density. We manipulated interference by altering
the size of the patches: two small (high aggression/interference) or two large (low
aggression/interference) patches. Birds preferred to feed at the rich patch when patches
were large and fighting infrequent. Birds aggressively interfered with each other at small
patches. As predicted, birds increased their use of poor patches to minimize interference
with half the birds feeding at the rich patch and the other half at the poor patch. Our study
is the first to support the Interference IFD prediction that consumer distributions can
become independent of resource distribution.

Sheep self-medicate when challenged with illness-inducing foods

sdduncan_manager — 2006-08-02T20:33:03Z

People learn to take aspirin for headaches, antacids for stomach aches, and
ibuprofen to relieve pain, and we often obtain prescriptions from doctors for
medications. Many of the drugs we use come from nature’s pharmacy and it has
been argued the desire to take medicines is the greatest feature that
distinguishes humans from the rest of the animals. But can other animals learn to
write their own prescriptions? Research at Utah State University suggests they
can. In these studies, sheep learned that sodium bentonite alleviates an acid
stomach from eating too much grain, that polyethylene glycol neutralizes the
adverse effects of foods high in tannins, and that dicalcium phosphate counters
the effects of foods high in oxalates. These medicines also enabled sheep to eat
more food, much as humans eat antacids before a spicy meal so they can eat
more and prevent an upset stomach.

Movements of male sockeye salmon, Oncorhynchus nerka, on spawning grounds: the effects of in-stream residency, density, and body size.

sdduncan_manager — 2006-08-02T20:47:36Z

We recorded the daily movements of male sockeye salmon from three populations during
their breeding season. We examined how movement varied among streams, among years
within streams, among males of different sizes, and as a function of how long the fish had
been living in the stream. This approach revealed that: 1) in all three streams, male
movement decreased as a function of time on the breeding grounds and was very limited
in most cases, 2) movement patterns, particularly initial exploratory movement, differed
among streams and among years within a stream but were unrelated to density, and 3)
large and small males showed equally limited movements. Most movement occurred in
the first few days in the stream, after which males seemed to wait for new females to
arrive rather than seek them elsewhere in the stream. These restricted movements have important implications for the evolution of salmon populations.

Aggressive Experience Alters Place Preference in Green Anole Lizards (Anolis carolinensis)

sdduncan_manager — 2006-08-03T06:09:05Z

Males of many species establish exclusive territories. We used a conditioned place
preference (CPP) procedure to determine whether engaging in aggression, was rewarding
for male green anole lizards and to determine whether aggressive experience could alter
spatial/contextual preferences. We repeatedly exposed male anoles to a mirror (which
frequently elicits aggressive displays) or the back of a mirror in opposing sides of a CPP
apparatus that consisted of two contextually distinct chambers connected by a tunnel.
Control animals were exposed to the back of the mirror in both sides of the apparatus.
Following conditioning, animals that exhibited aggressive behaviour when exposed to the
mirror increased the amount of time they spent in the side of the apparatus paired with the
mirror while the preferences of non-aggressive and control animals remained unchanged.
These findings suggest that aggression-related reward could play a role in the formation
and/or maintenance of stable territories.

Mate Recognition in a Simultaneous Hermaphroditic Shrimp, Lysmata wurdemanni (Caridea: Hippolytidae)

sdduncan_manager — 2006-08-03T06:15:58Z

Male crustaceans must find and identify receptive females in order to mate successfully.
Sex recognition mainly depends on sex pheromones, which are detected by antennae and
antennules. Distance (soluble) pheromone has been well documented to mediate mating behaviors
of some decapod crustaceans. Contact pheromone (an insoluble coating on the body surface) have
been proposed, but never been confirmed, to be used by male decapod crustaceans to detect
females. Here we report for the first time the involvement of both distance and contact
pheromones in the mating processes of a decapod crustacean, Lysmata wurdemanni. Females can
only mate during the small window of the post-molt period, during which they secrete both
distance and contact sex pheromone to attract males. Male shrimp tracked, recognized and
courted the receptive female shrimp based on both distance and contact sex pheromones, but
responded aggressively to newly molted male shrimp. Male shrimp with their chemosensory
appendages ablated appeared unable to identify EP shrimp, and neither courted nor copulated
with them. The outer flagella of the antennules house the receptors of the distance pheromone
whereas both antennae and antennules can detect the contact pheromone. Shrimp can still mate
successfully without the distance pheromone.

Behavioural mechanisms of invasion and displacement in Pacific island Geckos (Hemidactylus): evidence for interspecific reproductive interference

lopierce — 2006-08-03T19:11:39Z

Invasive species are a growing threat to global biodiversity. The increase in human travel and shipping over the last century has brought many exotic species to new lands. Many are thriving in their new habitats and their negative effect on native species may not be fully apparent for decades to come.

A recent study by Liz Dame and Ken Petren at the University of Cincinnati attempts to understand the role of behavior in animal invasions. They use Pacific gecko lizards as a model vertebrate system because they are easy to study in a controlled lab or field setting. Geckos occur in and on human houses across the world, thus they are very comfortable around humans and their structures. This team was able to understand how aggressive behavior and mating behavior affect each species’ ability to gather food and tip the tables in favor of the invading species.

Many scientists suspect that invaders succeed because they are better competitors for food, or because they are more aggressive and drive off native species. However, the Dame and Petren study suggests that something else is going on in their geckos. The invasive house gecko actually courts and mates with the native species. Although hybrids are not formed, some form of reproductive interference appears to be the most likely mechanism of displacement, because a number of other obvious possibilities were ruled out. Of course, it would be nice to extend these experiments to larger groups in a more natural setting, and that is the team’s plan. However this study clearly demonstrates that accounting for behavior will be a critical component in the goal to understand invasive species. It appears that it will be very difficult to predict or manage the affect of invasive animals without some knowledge of their behavior.

The queen is not a pacemaker in the small colony wasps Polistes instabilis and P. dominulus

sdduncan_manager — 2006-08-03T21:04:07Z

When individuals group together to rear young the work must be organized. In small social insect colonies it was thought that the queen orchestrated work, driving workers to forage, feed young, or build the nest. In this study we found otherwise. We observed natural colonies of two paper wasps, Polistes instabilis and Polistes dominulus. Work occurs in pulses, and who initiates activity can be said to be the orchestrator of work. A worker arriving at the nest or walking across the nest usually initiated these work pulses. The queen initiated no more pulses of activity than did the average worker. As there were far more workers than queens, this meant that nearly all active sessions were initiated by workers. These results change our view of the social integration in small wasp colonies. Their worker-initiated activity is like that of highly social colonies with thousands of wasps.

Inheritance of courtship song variation among geographically isolated populations of Drosophila mojavensis

sdduncan_manager — 2006-08-03T21:26:26Z

Many insect species communicate by means of acoustic signals. During courtship, males of many Drosophila species (sometimes called fruit flies) produce wing vibrations in order to achieve copulations. Thus, the acoustic properties of these male courtship songs are of great interest in terms of attractiveness to females, and possible differences in male mating success. These acoustic signals sometimes are used to avoid mating with the wrong species, or used by females to choose among potential mates with certain favorable song properties. Analysis of D. mojavensis songs has shown that this Sonoran Desert species is characterized by different songs in different parts of its species range. Study of male song differences was initiated to determine if they might be responsible for causing differences in mate choice among populations in addition to other signals exchanged between males and females during courtship. A genetic analysis of song differences was also performed.

Rhesus Monkeys (Macaca mulatta) Know What Others Can and Cannot Hear

sdduncan_manager — 2006-08-05T19:04:48Z

Although many animals use auditory information to functionally deceive other individuals, there has to date been little empirical verification that animals recognize how manipulating auditory information can alter what other individuals hear and know. Santos and colleagues are the first to show that at least one animal— the rhesus monkey (Macaca mulatta)— recognizes the connection between hearing and knowing. They presented monkeys with the opportunity to take grapes from a human competitor who was looking away. One of these two grapes was placed inside a silent container, while the other was placed inside a noisy container. Monkeys reliably took the grape from inside the silent container when the competitor was not looking, but not when the experimenter was looking and therefore already knew about the subject’s approach. These results demonstrate that monkeys preferentially attempt to obtain food silently only in conditions in which silence was relevant to obtaining food undetected.

On the evolution of hidden leks and the implications for reproductive and habitat selection behaviours

sdduncan_manager — 2006-08-05T19:10:57Z

Aggregations occur in all animal taxa, from insects to ungulates, and these aggregations can have
profound consequences for the ecology and evolution of organisms. While individuals might
have many reasons for being attracted to each other, an important link between mating strategies
and aggregations has not been adequately explored. In species with social pair bonds, infidelity
is common and results in ‘extra-pair’ copulations and paternity. The hidden lek hypothesis
suggests that aggregations of territorial males can result from female receptivity to extra-pair
copulations. We adapt four common models for the evolution of leks (aggregations of males that
females visit only for mating) to better understand the formation of hidden leks. Elaboration of
these models suggests distinct predictions that can be tested in situations where animals
aggregate in search of extra-pair copulations. Understanding the forces that shape hidden lek
formation and maintenance promises insight into habitat selection, aggregation, and reproductive
behaviours.

Prey crypticity reduces the proportion of group members searching for food

sdduncan_manager — 2006-08-05T19:20:43Z

Cryptic coloration protects against solitary predators but its efficiency against social predators is untested. Social predators are peculiar because they have the option of searching for their own food or exploiting others’ food. Consequently a group is a mixture of food searchers and exploiters. Using flocks of nutmeg mannikins we tested the hypothesis that cryptic coloration increases the predator’s search costs leading to lower proportions of searchers within groups. When we placed clumps of white millet seed on a background that made them cryptic, flocks of mannikins took longer to find the food, made more detection errors and significantly reduced the proportion of birds engaged in searching in three of four flocks. We conclude that
cryptic coloration provides a greater reduction in predation pressure when predators happen to be social because fewer social predators search for cryptic than non-cryptic prey.

Ecological and social influences on the hunting behaviour of wild chimpanzees (Pan troglodytes schweinfurthii)

sdduncan_manager — 2006-08-07T05:31:35Z

We used 25 years of data from Gombe National Park, Tanzania, to examine the factors affecting male chimpanzees’ decision to hunt red colobus monkeys. Our results provide evidence against social explanations for hunting in favour of more simple ecological alternatives. Upon encountering red colobus monkeys, male chimpanzees were less likely to hunt if sexually receptive female chimpanzees were present, indicating that they were not seeking meat to trade for sex. Instead, they may be forced to choose between hunting and mating. Males did not seek meat to trade with other males for social support, and hunting probability was not affected by diet quality. Hunts were more likely to occur, and to succeed, in woodland than in evergreen forest, emphasizing the importance of visibility and prey mobility. Finally, per capita meat availability decreased with adult male party size, suggesting that males did not benefit nutritionally by hunting cooperatively.