The limited availability of refuges may represent an important factor promoting the evolution of sociality, particularly in bats. Spix’s disc-winged bats (Thyroptera tricolor ) show highly specialized morphological adaptations that enable individuals to roost inside furled musoid leaves. This roosting ecology presents major challenges, as leaves rapidly unfurl,forcing bats to locate new roosts on a daily basis. Despite the reliance of T. tricolor on such ephemeral roosting resources,bats form stable group associations. In this presentation, I will discuss work done by myself and Dr. Karina Montero,which focuses on characterizing the behavioural patterns and communication strategies use by this species, which somehowmaintains high group cohesion while moving to a new roosting location on a daily basis. In the first study presented,video and acoustic monitoring was used to assess how groups identify suitable leaf roosts and determine if acousticsignals facilitate group interactions during nightly activity. In the second study, patterns of geographic variation inthe acoustic features of two contact calls were compared with patterns of genetic differentiation of two Costa Rican populations separated by a mountain range. In the third study, an automated telemetry system was used to examine thenocturnal movement patterns of group members to determine the patterns of space use and dyadic interactions. Overall,this work contributes to our understanding of the behavioural strategies used by free-ranging bats to maintain contactwith group members and provides insight into the role of shelter stability in the evolution of the T. tricolor social system. [more]

Animals evolved sexual displays to attract partners, but these communication signals can also attract unwanted eavesdroppers imposing substantial costs that may outweigh their benefits. Furthermore, the production of many signals generates additional cues that can be picked up through a wide range of sensory systems, which needs to be taken into account when trying to understand how signals evolved and how they will respond to environmental changes. I study the sexual advertisement call of the tungara frog (Physalaemus pustulosus), a species that calls while floating in shallow puddles in the Panamanian rainforest. Calling behaviour is under strong sexual selection from females as well as natural selection from multiple eavesdroppers. Additionally, the production of these calls is associated with a large vocal sac which movements generates visual cues, as well as water surface waves or ripples that travel throughout the puddle. I will show how eavesdroppers, such as rival males or predators can use these additional cues to locate a calling male. Furthermore, I will highlight the different sensory systems used as well as the role of the environment in driving selection pressures on production and transmission of signals and their by-product cues. Finally, I will discuss the concept of multimodal ecology and its importance when trying to understand the role of sensory pollution in an urbanizing world. [more]

Bat wings evolved from grasping, manipulating mammalian hands, and this origin influences the biomechanics of flight in bats in comparison to flight in birds and insects. Therefore, an evolutionary perspective is critical to advancing the comparative biology of flight, and helps distinguish those aspects of flight that are shared in all flying animals and those features that are unique to bats. Low weight, particularly in the wings, is important for all flying animals, but selection for reduced wing mass in bats must interact with aspects of neural control in the most morphologically complex of animal wings. In addition, the nature of wing skin as a complex functional material and the capacity to modulate wing mechanical properties during flight by an unusual group of muscles found only in bats proves critical to bat flight performance. Improved understanding of the functional architecture of bat wings not only provides insight into steady-state flight behaviors, but also holds promise for solving problems concerning bats’ abilities to recover from perturbations, fly effectively even following wing damage or injury, etc. This approach requires sophisticated bioengineering techniques such as particle image velocimetry, multi-camera high speed videography, and dynamic modeling, but also low-tech methods including polarized light photography, histology, and anatomical description. [more]

Food sharing in vampire bats has been a classic textbook example of “reciprocal altruism”, or reciprocity. In the last two decades, however, evidence of reciprocity in nonhuman animals has been much debated. In this talk, I review the current evidence for and against the importance of reciprocity in food sharing among both kin and nonkin vampire bats. Fasting trials with familiar captive bats show that reciprocal sharing is more important than kinship for predicting food sharing and for predicting attraction to playback of contact calls. Power-analysis simulations using behavioral data from vampire bats (563 observations, 36 individuals), mandrills (1703 observations, 10 individuals), and macaques (737 observations, 22 individuals) show that kinship effects can mask reciprocity, even when reciprocal help is more predictive. This is because, the precision of kinship estimates is independent of the number of behavioral observations that accumulate, so nepotism is detected earlier and symmetrical sharing between kin is counted as evidence for kinship bias, not reciprocity, in a linear model with both kinship and reciprocal help as factors. Both food-sharing and allogrooming rates are responsive to experimental manipulations of neuroendocrinology, social experience, donor costs and receiver benefits. Most notably, exclusion experiments show that helping kin yields greater inclusive fitness benefits per capita, but helping nonkin creates more ‘backup’ partners that allow bats to cope better with loss of primary donors. Current work is tracking how food-sharing bonds form between previous strangers. In summary, several lines of evidence support the reciprocity hypothesis, but it has yet to be demonstrated that reducing cooperative returns from a specific partner reduces a bat’s food-sharing rates to that partner. Finally, I discuss evidence that food-sharing is one part of a long-term cooperative relationship that may provide other social benefits. [more]

The structure from motion problem in computer vision is the problem of determining camera position and orientation as well as the 3D positions of scene features using the motion of image features only. The analogous problem for audio and radio is the problem of determining sender and receiver positions using the received audio or radio signal only. For both video, audio and radio there are a number of challenges, e.g. feature detection, robust feature matching and robust parameter estimation. The problem is challenging also because of the non-linear nature of the problem. In the talk a summary of results of both theoretical and applied nature is presented. [more]

Echolocation is a process where bats and toothed whales must emit sound to generate echoes returning to their auditory systems for processing, meaning that they control sensory information flow by the rate, type and direction of the sounds they produce as well as by adjusting the sensitivity of their hearing. These parameters directly influence the temporal resolution and spatial extent of their perception of their environment, enabling dynamic control of attention in response to environmental complexity and behavioral objectives. Thus, the way that echolocating animals manipulate their perception of the surrounding environment is revealed by the sonar pulses they emit, the echoes they receive and the evoked behavioral changes; all of which can now be sampled by small archival tags attached to both bats and toothed whales during dark hunts in the wild. It appears that this form of active sensing in two very different media of air and water show a remarkable level of functional convergence in terms of sampling rates, acoustic gaze adjustments and frequency ranges. Conversely, in other aspects of their sensory ecology, bats and toothed whales diverge by having extreme versions of reactive versus deliberate modes of sensory-motor operation due to very different relationships between sensory volume and forward speed. I will argue that echolocating bats and toothed whales are ideal experimental models for studying sensory and cognitive adaptations that confer advantages in handling a dynamic sensory umwelt in time and space, providing a unique, non-invasive insight into perception in naturally behaving animals. [more]

Bats and insects have been battling in the night sky for at least 60 million years -- In this talk, I will reveal some of the anti-bat strategies that insects have evolved to thwart the very sensory systems of the predators that hound them. [more]

The neotropical insectivorous bat, Thyroptera tricolor, or Spix’s disc-winged bat, is known to form extremely cohesive social aggregations despite moving daily between roost-sites. My research over the last 13 years shows that T. tricolor uses a combination of two social signals, “inquiry” and “response” calls, to locate each other during flight and while roosting. In my talk, I will focus on the role that these social calls play in maintaining cohesive groups, and the causes and consequences of the variation in vocal behavior we see within and among groups. [more]

Chemically defended animals often display conspicuous colour patterns that predators learn to associate with their unprofitability and subsequently avoid. Such animals, known as aposematic, deter predators by stimulating, for example, their visual and chemical sensory channels. Thus, aposematism is considered to be ‘multimodal’, which is advantageous because multimodal signals provide to the receiver more information per unit of time than unimodal signals. Despite this being widely known, the different components of aposematic signals tend to be studied in isolation, with most studies focusing on visual signals. Novel signals of aposematic prey are expected to be selected against due to positive frequency-dependent selection, but nature has a wide range of examples of variation among aposematic prey which contradict evolutionary expectations and leave us wondering how this variation can arise and persist. Using a polymorphic tiger moth (Arctia plantaginis) and a polytypic poison frog (Dendrobates tinctorius), we explore the forces of selection on variable aposematic signals at different scales, and study predator response to the visual and chemical components of their multimodal warning signals. Our findings in both systems highlight the importance of accounting for variation in both components of multimodal aposematic displays, and, most importantly, of testing whether or not relevant predators react differently to this variation, as they are the ultimate selective agents in predator-prey systems. [more]

Successful acoustic communication requires sender (sound production) and receiver (sound perception) to be attuned. With more than 7000 species, bushcrickets are a highly diverse group with a remarkable variability in their acoustic behaviours that often show asymmetrical signalling between males and females. In our comparative studies we examined sound production and sound perception in different bushcricket species to investigate if sex-specific signalling differences are also reflected in the morphological structures and physiological responses of the hearing organs. Our anatomical, biomechanical and neurophysiological data revealed pronounced and behaviourally relevant differences in the sender and receiver structures in the two different species. Furthermore, we discovered a sex-specific auditory fovea in the ears of male Ancylecha fenestrata that is tuned to the dominant frequency of the female call. Population coding by similarly tuned afferent projections from the ears may provide hyperacute temporal signal information, which is currently under further investigation. [more]

Crickets use sound to find each other space over which potential mates can sense each other is determined by the loudness of song and the sensitivity of the auditory system. According to the textbooks, this space is enhanced purely ‘passively’ through morphology and mechanical resonance. Song producting wings and females ears resonate at the same frequency enhancing the size of their acoustic space. But some crickets didn’t read the textbook. In this talk, I will present my research on Oecanthus henryi which is one such species. O. henryi is a tree cricket, and males of this species use an active behavioural strategy to make themselves louder. They manufacture an acoustic baffle, a tool that makes them louder. In fact, using a series of models and experiments, we showed that not only do they manufacture a tool, but they manufacture an optimal tool. Not to be outdone, we found that O. henryi females, have an active physiological amplification system in their ears. Using careful neurobiology we show that the amplifier doesn’t actually make them more sensitive than other crickets, as previously speculated. Rather, it allows them to change the frequency that they are sensitive to. What is even more remarkable is that this amplification is acheived through the activity of only a handful of motors protein. Both findings underline the poverty of our descriptions of invertebrate behaviour and biophysics, and point to a wealth of innovations yet to be discovered even among these ‘simple’ organisms. [more]