Research

Antipredator Behavior and Coloration in Striped Skunks

Striped skunks (Mephitis mephitis) are found throughout the United States and are known around the world for their bold color patterns and noxious spray defenses. As a model system for aposematism and defensive behavior in mammals, striped skunks' notorious noxious spray defenses are advertised by bold black-and-white coloration and signaled behaviorally by tail erection, foot stomping, charging, hissing, and aiming. The sprayed liquid is a mixture of sulfur-containing compounds that are produced in the anal glands and sprayed out papilla just inside the sphincter. These thiols are horribly powerful when they contact the eyes and nose of potential predators, especially dangerous mammalian carnivores like coyotes and mountain lions. For this reason, skunks are rarely if ever attacked and killed by other mammal predators, and their main source of predation comes from owls, which have reduced senses of smell and can fly in and attack silently from above. In our lab, we are interested in studying how these defenses evolved, how much do they vary between individuals, how do stripe patterns co-vary with noxiousness as a measure of signal honest, and how does having a powerful defensive weapon influence perceptions of fear in skunks. We approach these questions in a variety of ways. First, we have an ongoing 5-year skunk trapping project where we can mark, measure, sample, track, and collect anal secretions from wild skunks. Second, we conduct experiments of skunk behavioral responses to predator cues in the wild (visual, auditory, and olfactory), including the use of our robotic "Obi-Wan Coyote" model. Third, we conduct museum studies of skunk pelts to study how their coloration varies over space and time and the mechanical properties of the the color signal.

 

Urban Predator Ecology and Behavior

The loss and fragmentation of natural habitats that results from anthropogenic land development have been associated with reductions in biodiversity. Some Carnivorans adapt very well to living in urban landscapes, able to den in and move through fragmented natural areas and feed on natural prey, garbage, and free-living domestic pets. Large, wide-ranging predators like mountain lions (Puma concolor) are particularly vulnerable to the effects of urbanization and are becoming increasingly rare throughout southern California. However, the effects of urbanization are not the same for all species; the North American home range of coyotes (Canis latrans) for example, has expanded despite urbanization, their presence in urban landscapes being attributed in part to behavioral adaptations that allow them to exploit anthropogenic food sources and structures. We are studying how coyotes (Canis latrans) and other predators move through urban landscapes, feed on different types of prey, and interact with domestic pets. We are working toward these goals in three distinct ways:

1) The Mammal Lab is a partner in the Urban Wildlife Information Network, an enormous collaboration between more than a dozen educational and wildlife institutions to study how wildlife activity changes along an urban to rural gradient. As a partner, we have set up more than 25 motion activated trail cameras in Orange County, CA to monitor wildlife activity. In addition to sharing our data with our partners, we are asking questions about how urbanization influences local carnivore activity, particularly urban coyotes. We are interested in collaborating with local and national partners to broaden our work on coyote ecology in urban landscapes.

2) We also use motion activated trail cameras to study wild predator interactions with prey models. Specifically, we are interested in how coyotes interact with (i.e., avoid, investigate, are attracted to) artifical furry skunk models that have different stripe patterns and scents associated with them. By observing natural spontaneous encounters with our models, we can study how different signals from the skunks influence coyote predatory behavior.

3) In collaboration with Utah State University, we have been conducting experimental studies of coyote predatory and learning behavior on captive coyotes at the USDA Predator Research Center in Logan, Utah. Using artifical furry models that vary in coloration and may or may not spray noxious skunk oil, we can ask questions about how individual naive coyotes learn about skunk defenses and their ability to generalize negative experiences to new encounters with other skunks that might vary in their patterns. Further, we ultimately hope to use our knowledge of aversive learning in coyotes to explore the potential of training wild coyotes to not attack domestic pets and ease human-wildlife conflict.

Evolution of Antipredator Behavior, Defensive Weaponry, and Aposematism

Specialized morphological defenses and weaponry help prevent injury upon attack and/or improve ones chances of finding a mate, and such traits are found in some members of nearly every animal group. Defenses usually take the form of thickened tough skin, hard armored shells or exoskeletons, sharp spines, noxious sprays, or toxic secretions. Clearly some taxa invest a great deal in body armor while others favor other antipredator strategies (crypsis, aposematism, rapid escape, specialized refuge use) – we don’t know what influences the evolution, maintenance, or diversity of morphological defenses. Sexual weaponry may be seasonal or carried permanently all year, but weapons like antlers, horns, and tusks are certainly costly to construct and maintain. For both armor and weaponry, we are interested in the factors that promote their evolution and effects they have on other aspects of morphology, life history, physiology, or behavior. We are interested in how certain antipredator behaviors and morphological characters evolve together, or how the presence of one influences the other. Currently, we are exploring the evolution of spines and armored plates across all mammal groups, bold black-and-white coloration in carnivores, the evolution of tusks in ungulates, and the biomechanical properties of dermal armor in armadillos and pangolins. Working with preserved skins and skulls in natural history museum collections as well as books and photographs found online, this research uses phylogenetic analyses of antipredator behavior, coloration, and physical defenses in hopes of discovering what morphological and environmental factors facilitate the evolution of antipredator behavior.