Apr 2010: Rex Cocroft, University of Missouri
Collective anti-predator signaling in treehopper broods
In thornbug treehoppers (Hemiptera: Membracidae), females defend a cluster of stationary offspring against predators. Females must approach the predator to defend the brood, and offspring produce collective signals that reveal not only the predator's presence, but also its location. A computational model of collective signaling in these groups suggests that a few informed individuals, along with positive feedback and appropriately tuned response thresholds, are sufficient to produce informative group signals. The presence of two signal components (one tactile, one substrate-borne) with different active spaces allows the integration of both local and global cues about the decisions of other group members. Offspring signaling thresholds are lowered during the course of a predator encounter, but maternal signals produced after the encounter raise thresholds back toward baseline levels. Unresolved issues include the means by which females integrate the information contained in offspring signals; the significance of sporadic individual signaling in the absence of a predator; and the contrast between the high-gain system in this species, in which a few individual signals can quickly lead to signaling by the entire group, and the low-gain system present in a closely related species.
9 Apr 2010: Alexander (Sandy) Harcourt and Kelly Stewart, University of California - Davis
Conserving gorillas: How threatened are they really?
Gorillas no doubt face many threats.
But how threatened are they really? We suggest that the degree of threat might be overstated, including by the widely used IUCN Red List. In the recent (2010) UNEP report, the degree of threat is grossly and dangerously overstated. Athropomorphism, politics, lack of data, and ignoring of the most useful data are some of the suggested problems. One of the items of data ignored is the extraordinary success of mountain gorilla conservation, which in its new direction of improvement of health of the local people illustrates in microcosm the global success of biodiversity programs as measured by indices of poverty alleviation.
16 Apr 2010: Yossi Yovel, Department of Neurobiology, Weizmann Institute of Science, Israel
Strategies for optimal sensory acquistion in echolating bats
In my talk, I will present data showing that echolocating bats are an excellent animal model for quantitative and computational studies of animal behavior. Echolocating bats perceive their surroundings acoustically. They repetitively emit ultrasonic sonar signals and analyze the returning echoes in order to orient in space and acquire food in complete darkness. Natural echoes comprise a major part of the bat's sensory world, and have likely played a key evolutionary role in shaping the design of the bat's echolocation system and the auditory computations in the bat brain. However, the statistics of natural complex echoes, as well as how bats utilize them, are poorly understood. In the first part of the talk I will focus on natural stimulus statistics in the auditory modality (statistics of echoes) and the ability of bats to classify them. In the second part of the talk I will present a novel and surprising behavioral strategy that we found in Egyptian fruit bats, which we show is optimal for localizing and tracking a stimulus. This strategy consists of placing the maximal slope of the sonar beam onto the target, which is most sensitive to changes in target location. Moreover, experiments under two conditions of signal-to-noise ratio (SNR) reveal that bats choose to use this "slope strategy" in high-SNR conditions, but use an "optimal-SNR strategy" (placing the peak of the sonar beam onto the target) under low-SNR conditions. We suggest that this tradeoff between SNR and localization is fundamental to sensory systems in general, and is likely relevant for other modalities and organisms.
Reference: Yossi Yovel, Ben Falk, Cynthia F. Moss and Nachum Ulanovsky (2010) Optimal localization by pointing off axis. Science 327 (5966), 701-704.
23 Apr 2010: Frank Heppner, Department of Biological Sciences, University of Rhode Island
Forty years of organized bird flight studies
Other than a few sporadic observational studies, scientific examination of organized flight in birds didn't really begin until the early 1970's. There was more speculation than data in these early days, primarily due to limitations in technology. Computer analysis meant punching out thousands of IBM cards (now, fortunately, remembered by only a few). Super-8 movie film was cheap, but grain size was about as big as a bird. Grants were almost unknown, and there were many amateurs involved. Today, biologists, physicists, mathematicians, and computer scientists have been attracted to this phenomenon, which every layman has seen and marveled over, and is just now beginning to reveal its secrets and present practical applications.
30 Apr 2010: Kate Nowak
Behavioral flexibility and population persistence of a ‘specialist’ primate
Specialization has been suggested as a major correlate of extinction proneness in primates. The categories ‘generalist’ and ‘specialist’ appear to tell us little however about how primate species persist under habitat disturbance regimes while threatened or endangered, as demonstrated by a growing number of field studies documenting behavioral adaptations in so-called ‘specialists’. Colobus species, considered rare, specialized forest dwellers occupy a wide range of habitats and have group sizes that range from some of the smallest to the biggest recorded for any forest-living primate. More than half of the global population of the endangered Zanzibar red colobus lives outside one major protected area on Zanzibar Island, Tanzania. I present data on the behavioral diversity and flexibility in two subpopulations of Zanzibar red colobus inhabiting unprotected areas in two indigenous habitat types that differ floristically and in levels of human disturbance. Flexibility I generally define as the manifestation of previously unobserved behavior as based on prior studies conducted in the one protected area. The relationship between flexible behavior and the population dynamics of Zanzibar red colobus is explored. The role of Afrotropical mangroves as an important refuge for colobus, and other primate taxa, where terrestrial forests are disturbed is briefly discussed.
7 May 2010: Christie Riehl
Simple rules reduce conspecific brood parasitism in a cooperatively breeding cuckoo
The Greater Ani (Crotophaga major) is a Neotropical cuckoo that nests in groups composed of several socially monogamous pairs. All of the females lay their eggs in a single communal nest, and all group members contribute to incubation and parental care. In a four-year study of a color-banded, genotyped population of Greater Anis in Panama, we found that communal nests are frequently parasitized by extra-group females. Whereas group members typically lay their eggs in tight synchrony, the majority of nest parasites “dump” their egg in the nest several days later. A series of experiments confirmed that Greater Anis are incapable of recognizing parasitic eggs based on the genetic maternity of the egg, or on the number of eggs in the clutch. However, they can discriminate between freshly-laid eggs and those that have already been incubated, and accordingly eject asynchronous, parasitic eggs. This provides an empirical example of a complex, group-level behavior that arises through relatively simple “rules of thumb,” without requiring advanced cognitive mechanisms such as learning or counting.
14 May 2010: Qing Cao
What could we get from animal movement data?
Movement behavior is animal’s active adaptation to the environment. Unlike habitat selection analysis, movement analysis in time series could pick up the animal's movement rhythm and finer-scaled habitat use, as well as the key environmental factors and the temporal aspects that affect movement decision-making, which could be otherwise ignored. Przewalski’s Horses have been newly reintroduced to their original habitat in Central Asia, where they lack pre-existing global knowledge of the landscape. In contrast, a random-walking movement using local knowledge window could be observed from the telemetry data. The movement data allow us to see through these animals’ eyes, bring us close to the decision-making level of the animal movements and let us understand their habitat use with temporal dynamics. I will also discuss the potential conservation issues raised from their movement pattern and future research directions.
21 May 2010: Shermin de Silva, University of Pennsylvania
From individuals to societies: Socioecology of the Asian elephant
I present the first longitudinal study of social associations in Asian elephants (Elephas maximus), exposing the individual-level interactions that give rise to social structure. I examine whether social organization in a population of over 300 individually-identified elephants conforms to expectations based on the environmental constraints of predation and resource availability. While Asian elephants have lower rates of association than the African savannah elephant -- in conformity with expectations under the environmental constraints model -- lower association rates do not preclude the existence of complex extended networks of social affiliation, maintained through active communication.
28 May 2010: Mark Laidre
Culturally transmitted gestures in nonhumans? New experiments
This talk will involve substantial monkeying around, though of a serious, scientific kind. In it we will travel around the world examining the gestural communication of the largest of all monkeys, the mandrill (Mandrillus sphinx). Mandrill groups (20+) were studied throughout North America (USA and Canada), Europe (UK, Germany, and Italy), and in the species’ natural home range in equatorial West Africa (Gabon), for a sample of several hundred individuals observed across 8+ years. Our focus will be two unique gestures whose geographic distribution suggests they may be ‘cultural’. The first half of the talk will explore the form of these two gestures, their distribution within and across groups, their function, and their historical origin and spread. The second, more exciting part of the talk will sketch a series of controlled experiments (some in progress, others perhaps too logistically difficult and prohibitively expensive to ever envision they’ll actually make it to the ‘in progress’ stage). Nevertheless, the experiments are intended to address a tantalizing question that has never been definitively answered: can nonhuman animals culturally transmit their gestures?