Julie K. Young

The Evolution of Self-Control

Significance Although scientists have identified surprising cognitive flexibility in animals and potentially unique features of human psychology, we know less about the selective forces that favor cognitive evolution, or the proximate biological mechanisms underlying this process. We tested 36 species in two problem-solving tasks measuring self-control and evaluated the leading hypotheses regarding how and why cognition evolves. Across species, differences in absolute (not relative) brain volume best predicted performance on these tasks. Within primates, dietary breadth also predicted cognitive performance, whereas social group size did not. These results suggest that increases in absolute brain size provided the biological foundation for evolutionary increases in self-control, and implicate species differences in feeding ecology as a potential selective pressure favoring these skills. Cognition presents evolutionary research with one of its greatest challenges. Cognitive evolution has been explained at the proximate level by shifts in absolute and relative brain volume and at the ultimate level by differences in social and dietary complexity. However, no study has integrated the experimental and phylogenetic approach at the scale required to rigorously test these explanations. Instead, previous research has largely relied on various measures of brain size as proxies for cognitive abilities. We experimentally evaluated these major evolutionary explanations by quantitatively comparing the cognitive performance of 567 individuals representing 36 species on two problem-solving tasks measuring self-control. Phylogenetic analysis revealed that absolute brain volume best predicted performance across species and accounted for considerably more variance than brain volume controlling for body mass. This result corroborates recent advances in evolutionary neurobiology and illustrates the cognitive consequences of cortical reorganization through increases in brain volume. Within primates, dietary breadth but not social group size was a strong predictor of species differences in self-control. Our results implicate robust evolutionary relationships between dietary breadth, absolute brain volume, and self-control. These findings provide a significant first step toward quantifying the primate cognitive phenome and explaining the process of cognitive evolution.

Is Wildlife Going to the Dogs? Impacts of Feral and Free-roaming Dogs on Wildlife Populations

In human-populated landscapes, dogs (Canis familiaris) are often the most abundant terrestrial carnivore. However, dogs can significantly disrupt or modify intact ecosystems well beyond the areas occupied by people. Few studies have directly quantified the environmental or economic effects of free-roaming and feral dogs. Here, we review wildlife-dog interactions and provide a case study that focuses on interactions documented from our research in Mongolia to underscore the need for studies designed to best determine how dogs affect native wildlife and especially imperiled populations. We suggest additional research, public awareness campaigns, and the exclusion of dogs from critical wildlife habitat. The application of scientific findings to management and enhanced public outreach programs will not only facilitate recovery and maintenance of wildlife populations globally but also has the potential to reduce economic losses.

Protecting Migration Corridors: Challenges and Optimism for Mongolian Saiga

Hunting pressure and habitat loss place the endangered saiga, a type of antelope that was once abundant in central Asia, at high risk of extinction, and make the protection of the migratory routes of Mongolian populations even more critical for conserving the species.

Human disturbance influences reproductive success and growth rate in California sea lions (Zalophus californianus)

The environment is currently undergoing changes at both global (e.g., climate change) and local (e.g., tourism, pollution, habitat modification) scales that have the capacity to affect the viability of animal and plant populations. Many of these changes, such as human disturbance, have an anthropogenic origin and therefore may be mitigated by management action. To do so requires an understanding of the impact of human activities and changing environmental conditions on population dynamics. We investigated the influence of human activity on important life history parameters (reproductive rate, and body condition, and growth rate of neonate pups) for California sea lions (Zalophus californianus) in the Gulf of California, Mexico. Increased human presence was associated with lower reproductive rates, which translated into reduced long-term population growth rates and suggested that human activities are a disturbance that could lead to population declines. We also observed higher body growth rates in pups with increased exposure to humans. Increased growth rates in pups may reflect a density dependent response to declining reproductive rates (e.g., decreased competition for resources). Our results highlight the potentially complex changes in life history parameters that may result from human disturbance, and their implication for population dynamics. We recommend careful monitoring of human activities in the Gulf of California and emphasize the importance of management strategies that explicitly consider the potential impact of human activities such as ecotourism on vertebrate populations.

Production of Hybrids Between Western Gray Wolves and Western Coyotes

Using artificial insemination we attempted to produce hybrids between captive, male, western, gray wolves (Canis lupus) and female, western coyotes (Canis latrans) to determine whether their gametes would be compatible and the coyotes could produce and nurture offspring. The results contribute new information to an ongoing controversy over whether the eastern wolf (Canis lycaon) is a valid unique species that could be subject to the U. S. Endangered Species Act. Attempts with transcervically deposited wolf semen into nine coyotes over two breeding seasons yielded three coyote pregnancies. One coyote ate her pups, another produced a resorbed fetus and a dead fetus by C-section, and the third produced seven hybrids, six of which survived. These results show that, although it might be unlikely for male western wolves to successfully produce offspring with female western coyotes under natural conditions, western-gray-wolf sperm are compatible with western-coyote ova and that at least one coyote could produce and nurture hybrid offspring. This finding in turn demonstrates that gamete incompatibility would not have prevented western, gray wolves from inseminating western coyotes and thus producing hybrids with coyote mtDNA, a claim that counters the view that the eastern wolf is a separate species. However, some of the difficulties experienced by the other inseminated coyotes tend to temper that finding and suggest that more experimentation is needed, including determining the behavioral and physical compatibility of western gray wolves copulating with western coyotes. Thus although our study adds new information to the controversy, it does not settle it. Further study is needed to determine whether the putative Canis lycaon is indeed a unique species.

The Cost of Male Aggression and Polygyny in California Sea Lions ( Zalophus californianus )

In polygynous mating systems, males often increase their fecundity via aggressive defense of mates and/or resources necessary for successful mating. Here we show that both male and female reproductive behavior during the breeding season (June–August) affect female fecundity, a vital rate that is an important determinant of population growth rate and viability. By using 4 years of data on behavior and demography of California sea lions (Zalophus californianus), we found that male behavior and spatial dynamics—aggression and territory size—are significantly related to female fecundity. Higher rates of male aggression and larger territory sizes were associated with lower estimates of female fecundity within the same year. Female aggression was significantly and positively related to fecundity both within the same year as the behavior was measured and in the following year. These results indicate that while male aggression and defense of territories may increase male fecundity, such interactions may cause a reduction in the overall population growth rate by lowering female fecundity. Females may attempt to offset male-related reductions in female fecundity by increasing their own aggression—perhaps to defend pups from incidental injury or mortality. Thus in polygynous mating systems, male aggression may increase male fitness at the cost of female fitness and overall population viability.

Incorporating cold-air pooling into downscaled climate models increases potential refugia for snow-dependent species within the Sierra Nevada Ecoregion, CA

We present a unique water-balance approach for modeling snowpack under historic, current and future climates throughout the Sierra Nevada Ecoregion. Our methodology uses a finer scale (270 m) than previous regional studies and incorporates cold-air pooling, an atmospheric process that sustains cooler temperatures in topographic depressions thereby mitigating snowmelt. Our results are intended to support management and conservation of snow-dependent species, which requires characterization of suitable habitat under current and future climates. We use the wolverine (Gulo gulo) as an example species and investigate potential habitat based on the depth and extent of spring snowpack within four National Park units with proposed wolverine reintroduction programs. Our estimates of change in spring snowpack conditions under current and future climates are consistent with recent studies that generally predict declining snowpack. However, model development at a finer scale and incorporation of cold-air pooling increased the persistence of April 1st snowpack. More specifically, incorporation of cold-air pooling into future climate projections increased April 1st snowpack by 6.5% when spatially averaged over the study region and the trajectory of declining April 1st snowpack reverses at mid-elevations where snow pack losses are mitigated by topographic shading and cold-air pooling. Under future climates with sustained or increased precipitation, our results indicate a high likelihood for the persistence of late spring snowpack at elevations above approximately 2,800 m and identify potential climate refugia sites for snow-dependent species at mid-elevations, where significant topographic shading and cold-air pooling potential exist.

Factors affecting survival and cause-specific mortality of saiga calves in Mongolia

Abstract Factors affecting juvenile survival are poorly known in the worlds most northern antelope, the endangered saiga (Saiga tatarica), yet these factors are fundamental for understanding what drives population change. We monitored Mongolia saiga (S. tatarica mongolica) calves in Sharga Nature Reserve, western Mongolia, during 2008–2010. Our results showed that male and single calves were heavier than females and twins, respectively. However, we identified no significant differences in seasonal or annual survival rates between sexes or between singletons and twins. Litter size and birth mass varied among years, and there was a negative relationship between these variables. Survival of calves during the 1st year was best explained by the covariates of year and litter size (confounded with body mass), suggesting that interannual variation in environmental conditions influenced twinning rates and body mass, and might play a key role in 1st-year survival. We identified 3 sources of mortality—predation by raptors, foxes (red fox [Vulpes vulpes] and corsac fox [V. corsac]), and lynx (Lynx lynx). Most predation was attributed to raptors, such as golden eagles (Aquila chrysaetos) and cinereous vultures (Aegypius monachus). Our results point to both environmental and biotic factors affecting survival of juvenile saiga.

Does Spatial Structure Persist Despite Resource and Population Changes? Effects of Experimental Manipulations on Coyotes

Abstract We tested the influence of a change in food resource distribution on space use and diet of coyotes (Canis latrans). We focused on 2 facets of space use: maintenance of home ranges by residents, and establishment of home ranges by immigrants after a coyote removal program. The study was conducted on 2 populations of coyotes in southern Texas. In both populations, a clumped, high-quality food source was added to randomly selected feeding stations to measure the influence of food distribution and abundance on home-range patterns, trespassing rates, and consumption of native prey. In established home ranges, coyotes visited and foraged at stations regularly and were found closer to stations during the treatment period. Although there was no overall treatment effect on home-range size (F = 1.66, d.f. = 5, P = 0.15), home ranges without supplemental food remained stable in size, whereas home ranges that had received supplemental food increased during the posttreatment period (t = 2.09, d.f. = 1, P = 0.04). Core areas showed a similar trend; there was no overall treatment effect (F = 1.51, d.f. = 2, P = 0.24); however, core areas of home ranges that received supplemental food were smaller than those of controls during the treatment period (t = 2.71, d.f. = 1, P < 0.01). There were no statistical differences in occurrence of any species, such as small mammals or white-tailed deer (Odocoileus virginianus), in scats of treatment versus control coyotes. Coyotes within the study site after removals were located closer to feeding stations during treatment than posttreatment (F = 8.83, d.f. = 1, P < 0.02, n = 897) periods, yet home-range size with supplemental food was larger than home-range size during the posttreatment period. Our findings suggest that a resource other than food influences coyote spatial patterns.

Weak polygyny in California sea lions and the potential for alternative mating tactics

Female aggregation and male territoriality are considered to be hallmarks of polygynous mating systems. The development of genetic parentage assignment has called into question the accuracy of behavioral traits in predicting true mating systems. In this study we use 14 microsatellite markers to explore the mating system of one of the most behaviorally polygynous species, the California sea lion (Zalophus californianus). We sampled a total of 158 female-pup pairs and 99 territorial males across two breeding rookeries (San Jorge and Los Islotes) in the Gulf of California, Mexico. Fathers could be identified for 30% of pups sampled at San Jorge across three breeding seasons and 15% of sampled pups at Los Islotes across two breeding seasons. Analysis of paternal relatedness between the pups for which no fathers were identified (sampled over four breeding seasons at San Jorge and two at Los Islotes) revealed that few pups were likely to share a father. Thirty-one percent of the sampled males on San Jorge and 15% of the sampled males on Los Islotes were assigned at least one paternity. With one exception, no male was identified as the father of more than two pups. Furthermore, at Los Islotes rookery there were significantly fewer pups assigned paternity than expected given the pool of sampled males (p<0.0001). Overall, we found considerably lower variation in male reproductive success than expected in a species that exhibits behavior associated with strongly polygynous mating. Low variation in male reproductive success may result from heightened mobility among receptive females in the Gulf of California, which reduces the ability of males to monopolize groups of females. Our results raise important questions regarding the adaptive role of territoriality and the potential for alternative mating tactics in this species.