Research in our lab aims to address some big questions about the evolution of animal communication. We are particularly interested in understanding how selection acts on signals in the real world, where signals vary in multiple dimensions both within- and between-individuals, the environment is noisy, and individuals sometimes make irrational or otherwise less-than-ideal decisions. Here are some things we've been up to recently.
Acoustic Communication in Frogs
During their breeding season, male frogs and toads gather in dense breeding aggregations and produce advertisement calls. Females use these vocalizations to discriminate among potential mates and thereby exert selective pressure on males and their signals. The signals of Cope's gray treefrog are variable within- and among-males in multiple dimensions, including call duration, call rate, pulse rate, dominant frequency and relative amplitude, traits for which females show pronounced preferences. I use phonotaxis (movement toward sound) behavior to study mate choice and the evolution of sexual signals by female mate choice. One of our major interests lies in understanding how signals evolve when receivers impose selection on multiple dimensions of the signal at the same time (Tanner et al. 2017, Evolution). Additionally, males display remarkable within-individual variation in signal properties, which we have shown is uncorrelated to male size or body condition (Tanner and Bee 2019, Behavioral Ecology). Females have pronounced preferences against high levels of within-individual variation for some call properties, but not others (Tanner and Bee 2020 Frontiers in Ecology & Evolution). Furthermore, female preferences for non-arbitrary signals of male quality erode when those signals contain natural levels of within-individual variation (Tanner and Bee 2020 Science Advances). Our work on the evolution of acoustic communication in treefrogs explores the importance of within-individual variation to the evolution of signals with different functions, and the consequences of that variation in signal production for population-level selection on mean call traits.
This slideshow contains images taken during field collections of treefrogs from breeding ponds at night.
This slideshow contains images taken during field collections of treefrogs from breeding ponds at night.
Evolution of Sexual Signaling in Crickets
Teleogryllus oceanicus, the Pacific field cricket, was introduced on Hawaii, where it co-occurs with a parasitoid fly, Ormia ochracea. Gravid female flies locate calling male crickets by their song and deposit larvae on them. Fly larvae develop inside the cricket, eating his organs and finally killing him when they emerge to pupate. This natural selection disfavors calling by male crickets, but song is strongly favored by sexual selection, because acoustic signals are the only long-range means of advertisement. This is an interesting system to explore the evolution of mating behavior because natural selection and sexual selection oppose each other. Work in Pacific field crickets has aimed at measuring the strength of sexual selection on the ability to sing in Hawaiian populations (Tanner et al. 2019, Evolution), the effect of prior experience of song quality on the expression of mating preferences in adult females, and how the prior mating experience of females affects mating decisions (Tanner et al. 2019, Animal Behaviour). We are also interested in understanding conflict between pre- and postcopulatory mechanisms of sexual selection in this system.
Effect of UAV Presence on American Black Bears
Unmanned aerial vehicles (UAVs, aka "drones") are increasingly popular tools for wildlife biologists to monitor populations. However, because drones are more maneuverable than other aircraft and not subject to the same altitude limitations imposed by law, they are noisy and potentially stressful to wildlife. With colleagues at the University of Minnesota, including Drs. Mark Ditmer, John Vincent, and Leland Werden, we investigated whether American black bears showed behavioral or physiological signs of stress in response to overhead flight of drones. We showed that wild bears had physiological, but not behavioral, signs of stress in response to drone presence (Ditmer et al. 2015, Current Biology). A follow-up study on captive bears showed that individuals habituated to repeated exposure to overhead drone flights (Ditmer et al. 2019, Conservation Physiology). As drones become more popular for recreation, photography, anti-poaching efforts and wildlife surveys, further research will be needed to assess their impact on animals.
Photos depict field work on wild bears in northwestern Minnesota.
Photos depict field work on wild bears in northwestern Minnesota.
Evolution of the Mammalian Baculum
A microCT image of the pelvic girdle in the house mouse, Mus musculus. The "floating" bone on the right side of the image is the baculum, or penis bone.
Ongoing work on the evolution of the baculum (penis bone) seeks to integrate insights from experimental evolution and phylogenetic comparative methods to understand genital diversification in rodents. Genital traits are among the most diverse and fastest evolving traits studied in animals, but we have little direct evidence about what drives their evolution in vertebrates. This work makes use of rodent specimens housed at natural history collections across Australia, recently developed methods for phylogenetic comparative analyses, and advanced imaging techniques.
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This work by Jessie C. Tanner is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.