Behavioural (Behavioral) Ecology

A Theoretical Approach to Study the Evolution of Aggregation Behavior by Larval Codling Moth, Cydia pomonella (Lepidoptera: Tortricidae)

by Alex Chubaty

Jumean Z, Ma BO, Chubaty AM, et al. (2011) Journal of Insect Behavior 24:249-263

Pupation site-seeking larvae of the codling moth, Cydia pomonella, aggregate in response to aggregation pheromone... more Pupation site-seeking larvae of the codling moth, Cydia pomonella, aggregate in response to aggregation pheromone produced by cocoon-spinning conspecific larvae. Larvae that pupate in an aggregation rather than in solitude may experience a lower rate of parasitism by the parasitoid Mastrus ridibundus. Additionally, adults eclosing from a larval aggregation may encounter mates more rapidly at the site of eclosion (on-site) than away from that site (off-site). We employed an evolutionary simulation to determine the effect of several ecological parameters on the evolution of larval aggregation behavior. These parameters included (i) the probability of mate encounter off-site; (ii) the time available for finding a mate; and (iii) the population density of parasitoids and their rate of larval parasitism. The model predicts that larval aggregation behavior is selected for when the probability of off-site mate encounter is low, the time to locate mates is short, and egg-limited parasitoids are at high population levels. We also show that aggregations reduce the risk of parasitism through dilution effects. The parameters found to favour the evolution of larval aggregation behavior are consistent with life history traits exhibited by C. pomonella.

A dynamic host selection model for mountain pine beetle, Dendroctonus ponderosae Hopkins

by Alex Chubaty

A.M. Chubaty et al. (2009) Ecological Modelling 220:1241–1250

The link between individual habitat selection decisions (i.e., mechanism) and the resulting population distributions... more The link between individual habitat selection decisions (i.e., mechanism) and the resulting population distributions of dispersing organisms (i.e., outcome) has been little-studied in behavioural ecology. Here we consider density-dependent habitat (i.e., host) selection for an energy- and time-limited forager: the mountain pine beetle (Dendroctonus ponderosae Hopkins). We present a dynamic state variable model of individual beetle host selection behaviour, based on an individual’s energy state. Field data are incorporated into model parameterization which allows us to determine the effects of host availability (with respect to host size, quality, and vigour) on individuals’ decisions. Beetles choose larger trees with thicker phloem across a larger proportion of the state-space than smaller trees with thinner phloem, but accept lower quality trees more readily at low energy- and time-states. In addition, beetles make habitat selection decisions based on host availability, conspecific attack densities, and beetle distributions within a forest stand. This model provides a framework for the development of a spatial game model to examine the implications of these results for attack dynamics of beetle populations.

The frontline of avian brood parasite–host coevolution

by William Feeney

Feeney, W. E., Welbergen, J. A., Langmore, N. E.

The interactions between avian interspecific brood parasites and their hosts provide tractable and informative systems... more The interactions between avian interspecific brood parasites and their hosts provide tractable and informative systems for investigating coevolution. Generally, these investigations have emphasized the egg and chick stages of the coevolutionary arms race; however, recent studies demonstrate that coevolution operates at all stages of the host nesting cycle and emphasize the importance of reciprocal adaptations prior to deposition of the parasite egg in the host nest: the ‘frontline’ of the arms race. Here we review the diversity of adaptations at the frontline and its implications for our understanding of brood parasite–host relationships. Coevolution at the frontline can fundamentally shape the life histories, morphologies, physiologies and behaviours of both brood parasites and their hosts, and influences the trajectories and outcomes of their subsequent coevolutionary interactions. We advocate the incorporation of frontline interactions in empirical and theoretical investigations of brood parasite–host arms races to provide a more holistic understanding of the coevolutionary processes in these systems.

From migration to nomadism: movement variability in a northern ungulate across its latitudinal range

by Luca Börger

Ecological Applications (in print) Co-authored with Navinder Singh (first author), Nils Bunnefeld, Holger Detki, and Goran Ericsson.

This is the first proper application of my net-squared displacement approach for modelling animal movements (Borger & Fryxell 2012).
#########################################

Understanding the causes and consequences of animal movements is of fundamental biological interest because any... more Understanding the causes and consequences of animal movements is of fundamental biological interest because any alteration in movement can have direct and indirect effects on ecosystem structure and function. It is also crucial for assisting spatial wildlife management under variable environmental change scenarios. Recent research has highlighted the need of quantifying individual variability in movement behavior and how it is generated by interactions between individual requirements and environmental conditions, to understand the emergence of population level patterns. Using a multi-annual movement dataset of 213 individual moose (Alces alces) across a latitudinal gradient (from 56° to 67° N) that spans over 1,100 km of varying environmental conditions, we analyze the differences in individual and population level movements. We tested the effect of climate, risk and human presence in the landscape on moose movements. The variation in these factors explained the existence of multiple movements (migration, nomadism, dispersal, sedentary) among individuals and seven populations. Hence, heterogeneity in the immediate environment can result in multiple movements within a species. Population differences were primarily related to latitudinal variation in snow depth and road density. Individuals showed both fixed and flexible behaviors across years, and were less likely to migrate with age in interaction with snow and roads. For the predominant movement strategy, migration, the distance, timing and duration at all latitudes varied between years. Males traveled longer distances and began migrating earlier in spring than females. Our study provides strong quantitative evidence for the dynamics of animal movements in response to changes in environmental conditions along with varying risk from human influence across the landscape. For moose, given its wide distributional range, changes in the distribution and migratory behavior are expected under future warming scenarios.

Mating behaviour of Sumatran rhinoceros. 1990.

by M.T. Abdullah, PhD

A Note on the Chance Preying by a Western Tarsier on Fruit Bats in Malaysian Borneo. 1998. MT ABDULLAH. Department of Zoology

by M.T. Abdullah, PhD

http://wps.prenhall.com/esm_freeman_biosci_1/0,6452,501302-,00.html

49.2 Predation

Predation in the Tarsier
Little is known about the predation and feeding behavior of the awkward looking primate, the western tarsier. This article outlines the research by Dr. M. T. Abdullah at University of Queensland in Australia, reporting on the predation of fruit bats by the tarsier. The article provides a great example of how biologists design studies to ask ecological questions about the relationship between predators and prey.
Keywords: predation, ecology, species interactions

Chance preying on bats by tarsier in Borneo. 1998. Chance preying on bats by tarsier in Borneo. 1998.

Seed predation by bonobos ( Pan paniscus ) at Kokolopori, Democratic Republic of the Congo

by Alexander Georgiev

Cynthia J. Moss, Harvey Croze, and Phyllis C. Lee (Eds.): The Amboseli Elephants: A Long-Term Perspective on a Long-Lived Mammal

by Alexander Georgiev

Plant food and tool transfer in savanna chimpanzees

by Jill Pruetz

Modelling evolutionarily stable strategies in oviposition site selection, with varying risks of predation and intraspecific competition

by Arik Kershenbaum

Many ovipositing mosquitoes, as well as other species, can detect biotic factors that affect fitness. However, a... more Many ovipositing mosquitoes, as well as other species, can detect biotic factors that affect fitness. However, a female mosquito seeking a high quality oviposition site (e.g. one with low risk of predation and competition to her progeny) must often balance the competing risk of increasing probability of mortality to herself while she continues to search, against increased probability of finding a high quality site. Such oviposition site selection may affect adult population size. We examined a female mosquito’s expected strategy of oviposition site selection under conditions of varying predator prevalence and adult mortality risk, by combining a detailed structured population model with a Markov chain implementation of the adult behavioural process. We used parameter values from the specific mosquito-predator system, Culiseta longiareolata-Notonecta maculata, although the overall results can be generalised to many mosquito species. Our model finds the evolutionarily stable strategy of oviposition site selection for different parameter combinations. Our model predicts that oviposition strategy does not vary smoothly with varying environmental risk of adult mortality, but that certain oviposition strategies become unstable at some parameter values. Mosquitoes will distribute their reproductive effort between breeding sites of varying predation risk only when adult mortality is low or larval competition high. Our model predicts that females will continue searching for predator-free pools, rather than oviposit in the first site encountered, regardless of the risk of mortality to the adult. The ecological basis for a reproductive strategy with alternative behaviours is important for understanding the effect of biotic factors on the population dynamics of mosquitoes, and for the development of biological control strategies, such as the dissemination of predator-cue chemicals.

The effect of female polyandry and sperm precedence on the evolution of sexual difference in dispersal timing: The evolution of sex-biased dispersal

by Tadao Hirota

The evolution of sex-biased dispersal by pre-dispersal copulation and fluctuating environment

by Tadao Hirota

Encounter-induced hostility to neighbors in the ant Pristomyrmex pungens

by Tadao Hirota

A COMPARATIVE STUDY OF DOLLAR COST AVERAGING VS. VALUE AVERAGING

by Pawel Stefan Benedykcinski

AUTHOR: PAWEL STEFAN BENEDYKCINSKI and ADVISOR: St. Olaf College ECONOMICS PROF. RICHARD GOEDDE

A COMPARATIVE STUDY OF DOLLAR COST AVERAGING VS. VALUE AVERAGING
Pawel S. Benedykcinski and Prof. Rick Goedde... more A COMPARATIVE STUDY OF DOLLAR COST AVERAGING VS. VALUE AVERAGING
Pawel S. Benedykcinski and Prof. Rick Goedde (Advisor)
Economics Department
St. Olaf College
Northfield, MN

My research compares three investment techniques, fixed and variable dollar cost averaging and value averaging to determine if any of the methods yield superior investment returns in the long run. Mutual funds, stocks, and exchange-traded funds were used to test the methods. Value averaging is a formula-based investment technique using a mathematical formula to guide the investment of money into a portfolio over time. With this method investors contribute to their portfolios in such a way that the portfolio balance increases by a set amount, regardless of market fluctuations. Dollar cost averaging invests equal amounts regularly and periodically over specific time periods in a particular investment or portfolio. By doing so more shares are purchased when prices are low, and fewer shares are purchased when prices are high.

After testing many mutual funds, ETFs, and individual stocks, I concluded that Value Averaging yields better Internal Rates of Return than fixed and variable Dollar Cost Averaging. The results also indicate that the three methods provide superior investment returns over extended investment time periods with little increase in risk, even if prices are volatile. One important difference between these three formula investment techniques is that value averaging requires larger sums of money to be invested at regular time intervals than fixed or variable dollar cost averaging do.

Food availability and offspring sex in a monogamous seabird: insights from an experimental approach

by Sarah Leclaire

Sex allocation theory predicts that parents should favor offspring of the sex that provides the greatest fitness... more Sex allocation theory predicts that parents should favor offspring of the sex that provides the greatest fitness return. Despite growing evidence suggesting that vertebrates are able to overcome the constraint of chromosomal sex determination, the general pattern remains equivocal, indicating a need for experimental investigations. We used an experimental feeding design to study sex allocation during 3 years in black-legged kittiwakes (Rissa tridactyla). Intense male–male competition for securing a breeding site is common in this species in which males are heavier and larger than females. Hence, we hypothesized that parents producing fledglings in better than average condition, as supplementarily fed pairs do, would increase their fitness return by producing sons. Conversely, producing daughters would be a better tactic for Unfed parents. Hence, we predicted that Fed parents produce more sons than Unfed parents. This prediction is particularly expected if sexual dimorphism arises as early as during chick rearing, suggesting strong selective pressures for optimal male development. Our results showed that 1) males were heavier and larger than females prior to fledging and that 2) Fed parents produced relatively more male hatchlings than Unfed parents. We interpret this result in terms of a Trivers–Willard-type process. Furthermore, our data revealed that Unfed parents significantly overproduced female hatchlings, whereas offspring sex ratio was balanced among Fed parents. Because the 3 reproductive seasons we considered were particularly poor food years, Unfed parents may have overproduced daughters to avoid the apparent higher reproductive costs of raising sons.

Private and public information use strategies by foraging groups of wild Siberian jays

by Irja Ida Ratikainen

Ratikainen, I. I., Sødal, L. R. H., Kazem, A. & Wright, J. (2012). Animal Behaviour. 83 (5) 1243-1251.doi: 10.1016/j.anbehav.2012.02.016

In variable environments variance-sensitive foraging should be replaced by more profitable sampling behaviour whenever... more In variable environments variance-sensitive foraging should be replaced by more profitable sampling behaviour whenever the variation in foraging rewards becomes predictable enough to track. We tested this suggestion in groups of wild Siberian jays, Perisoreus infaustus, during prewinter food-hoarding visits to experimental feeders. As predicted, all groups of jays switched to sampling once food items were clumped into ‘patches’ to create reliable patch-based information concerning prey sizes. However, increases in individual foraging success above chance were not achieved according to a simple ‘win-stay lose-shift’ rule of thumb. Instead jays employed a win-and-return-later strategy, returning more often over the experimental session to privately sampled patches containing the four largest of five prey sizes.
In contrast, public information that was gained by observing patch sampling by other group members involved a more gradual increase in the probability of patch use with the prey size involved. Use of public versus private information did not differ according to sex or social status. Even though the jays did not achieve the individually optimal strategy in this specific experimental set-up, their sampling behaviour using both public and private information are suggested to maximize both individual and group-wide foraging efficiencies when exploiting the ephemeral food sources typical of boreal taiga forests.

Male dimorphism of a neotropical arachnid: harem size, sneaker opportunities, and gonadal investment

by Roberto Munguia-Steyer

Munguía-Steyer, R., Buzatto, B. A. & Machado, G. 2012. Behavioral Ecology. doi:10.1093/beheco/ars037

Serracutisoma proximum is a harvestman with alternative male morphs. Large males use sexually dimorphic second legs in... more Serracutisoma proximum is a harvestman with alternative male morphs. Large males use sexually dimorphic second legs in fights for the possession of territories on the vegetation, where females oviposit. Small males have short second legs and do not fight but rather sneak into the territories and copulate with egg-guarding females. We investigated the presence of male dimorphism across 10 populations of S. proximum, compared gonadal investment between male morphs, and assessed if the distribution of the sneakers is influenced by harem size. In all populations, there was male dimorphism, indicated by the bimodal distribution of the leg II length/body length. Gonadal investment did not differ between morphs and was not affected by male size, second leg length, and morph relative frequency in the populations. We found 361 territories, 90.0% containing 1 male, 9.7% containing 2 males (dyads), and 0.3% containing 3 males. The probability of encountering dyads increased with the number of females present in the territories. Moreover, the proportion of sneakers in territories containing dyads was higher than would be expected by chance. One possible reason for the ubiquity of alternative morphs in S. proximum could be the high mating opportunities experienced by sneakers in spatially structured populations with a resource defense polygyny system. Additionally, the high frequency of successful invasions by sneakers and hence the high sperm competition risk for both morphs may explain the similarity in gonadal investment between male morphs.

Population growth, carrying capacity, and conflict

by Dwight Read

Co-authored with Steven A. LeBlanc. Published in Current Anthropology, 44(1), 2003, pp. 59-85

The standard model of population growth and regulation is critiqued.
It is argued that any model of population... more The standard model of population growth and regulation is critiqued.
It is argued that any model of population growth and regulation
must accommodate ten propositions, and a multitrajectory
model that does so is described. This model identifies
competition between groups, individual choice in reproductive
behavior, the scale for spatial and temporal variation in resource
abundance, and the social unit for resource access and ownership
as important components of population behavior.

Tasmanian knowledge and skill: Maladaptive imitation or adequate technology?

by Dwight Read

Published in American Antiquity, 7(1), 2006, pp. 164-184

A recent article has suggested that maintenance of complex tools and associated tasks in a group depends on the... more A recent article has suggested that maintenance of complex tools and associated tasks in a group depends on the presence of skilled individuals to serve as targets for imitation. The expected number of skilled target individuals, it is argued, relates to the population size. It is predicted that population size and maximum complexity of tools and/or tasks should correlate, hence a decrease in population size could lead to maladaptive loss of skills. Data from Tasmania are said to support the argument. However, the argument neither agrees with the archaeological data from Tasmania nor ethnographic observations on hunter-gatherer societies. Instead of being an example of a group that underwent maladaptive loss, the indigenous people of Tasmania appear to have used tools sufficient for the tasks at hand. An alternative model is proposed that distinguishes between motor skills and knowledge needed to do tasks effectively and takes into account assessment of the time cost for developing skills. Loss of skills more likely relates to change in the mode of resource procurement or change in technology rather than a shortage of skilled, target individuals due to decrease in population size.

A Non-Lévy Random Walk In Chacma Baboons: What Does It Mean?

by Cedric Sueur