Research in the lab is focused on animal behavior, with an emphasis on sensory ecology, animal communication, and conservation.
We are currently studying visual attention in peafowl. We know little about how animals shift their visual attention in naturalistic scenes. One potentially powerful method to identify how animals visually assess mates is with telemetric eye-tracking, in which a head-mounted infrared device tracks an animal’s gaze. This study has developed a lightweight telemetric eye-tracker for use on peahens that records their gaze. Using this system, the project will examine female gaze patterns and determine how these patterns relate to natural behavioral patterns.
Nocturnal antipredator behavior in peafowl (Pavo cristatus)
Although nocturnal predation is a major cause of animal mortality, antipredator behavior at night is poorly understood. To investigate how diurnal animals adjust their antipredator behavior during these different conditions, Michael Platt and I exposed peahens to a taxidermy raccoon during the daytime and nighttime. During the day, the peahens emitted loud antipredator calls, extended their necks upward, adopted a preflight posture, and approached the predator; at night, the peahens emitted soft hissing calls, remained stationary, piloerected their feathers, and raised their tails. The results demonstrate that birds adopt radically different antipredator behavior depending on whether the threat occurs in the daytime or nighttime. Videos showing nocturnal and diurnal antipredator behavior of peafowl are available online.
Mate-choice copying in humans
Mate-choice copying occurs when animals rely on the mating choices of others to inform their own mating decisions but the proximate mechanisms underlying mate-choice copying remain unknown. To address this question, Michael Platt and I tracked the gaze of men and women as they viewed a series of photographs in which a potential mate was pictured beside an opposite-sex partner; the participants then indicated their willingness to engage in a long-term relationship with each potential mate. We found that both men and women expressed more interest in engaging in a relationship with a potential mate if that mate was paired with an attractive partner. Men and women’s attention to partners varied with partner attractiveness and this gaze attraction influenced their subsequent mate choices. These results highlight the prevalence of non-independent mate choice in humans and implicate social attention and reward circuitry in these decisions.
Acoustic directionality in songbirds
Animals in many vertebrate species vocalize in response to predators, but it is often unclear whether these antipredator calls function to communicate with predators, conspecifics or both. Gail Patricelli and I evaluated the function of antipredator calls in songbirds by measuring the acoustic directionality of these calls in response to experimental presentations of a model predator. Acoustic directionality quantifies the radiation pattern of vocalizations and may provide evidence about the receiver of these calls.
Overall, the birds produce antipredator calls that have a relatively low directionality, suggesting that the calls radiate in many directions to alert conspecifics. However, birds in some species increase the directionality of their calls when facing the predator. They can even direct their calls towards the predator when facing lateral to it—effectively vocalizing sideways towards the predator.
Relaxed selection in pig-tailed langurs (Simias concolor)
Traits that were adaptive under previous conditions may no longer have fitness benefits. Thomas Ziegler and I studied the pig-tailed langur to determine whether this monkey still recognizes felids as predators even though dangerous felids do not exist on the islands on which it inhabits. We found that langurs fled more slowly and looked at the speaker less in response to the felid calls than they did in response to the calls of known predators (humans). The results suggest that langurs are afraid of novel vocalizations but have not retained specific acoustic knowledge of felid predator vocalizations.
Acoustic signalling in crows (Corvus brachyrhynchos)
Few studies have examined individual differences in the acoustic structure of mobbing and alarm calls. Sandy Vehrencamp, Ann Clark, Kevin McGowan and I explored individual differences in the acoustic structure of the inflected alarm caw of the American crow. We found that the acoustic structure of these calls differed across individuals and males had lower pitched calls than females. The results suggest that American crows have the potential to discriminate among individual birds on the basis of call structure alone.
In addition, little is known about how approach-inducing mob calls encode information about the predator type and the danger associated with it. Sandy Vehrencamp and I studied the mob calls of the American crow to determine whether these calls convey information about the predator type or the level of danger by presenting a model owl (representing an avian predator) and raccoon (representing a mammalian predator). We found that crows emit the same types of vocalizations in response to both of these predator classes. Our results, however, suggest that calls with a longer duration, higher rate, and shorter interval between caws reflect a higher degree of danger. The ability to encode specific information about urgency and individual or group identity while mobbing may be particularly important for efficient coordination of group activities in species—such as the American crow—that live in stable social groups.
Visual signalling in mandrills (Mandrillus sphinx)
The function of visual signals in animals is not always clear. Mark Laidre and I investigated the function of two visual signals of the mandrill (silent bared-teeth face and crest-raise). We found that both signals serve conciliatory functions, occurring most oftenin non-aggressive, non-hostile contexts, and represent a single graded signal.
Mark Laidre and I also exmained whether male mandrills offer parental care even though most male mammals do not provide such care. Male mandrills exhibited aggressive, protective behavior when definite or likely offspring became involved in agonistic confrontations with individuals outside of the group. The males also abandoned feeding opportunities, sexual consorts, and allogrooming sessions to intervene on behalf of their threatened offspring. The results suggest that male mandrills do provide paternal care to their offspring.
Furthermore, Sandy Vehrencamp and I investigated theantipredator behavior of mandrills. Predation has likely been a major selective force shaping the evolution of primates. As a result of this current and past force, primates display a variety of antipredator behaviors. We presented visual models of leopards and crowned hawk-eagles to semi-free ranging mandrills. We found that mandrills tended to respond appropriately to different predator stimuli by running into trees for leopard presentations and seeking cover for eagle presentations; the mandrills emitted alarm calls at higher rates and for longer amounts of time in the leopard presentations compared to the eagle presentations.