Using playback of territorial calls to investigate mechanisms of kin discrimination in red squirrels

A little while back, I did a Master’s degree at the University of Guelph with Prof. Andrew McAdam. I worked on the Kluane Red Squirrel Project, a collaborative project between several universities in Canada and the U.S. This long-term project was started nearly 30 years ago by Prof. Stan Boutin at the University of Alberta. The project has involved many undergraduate, graduates, and post-docs over the years studying a variety of ecological and evolutionary questions on a population of red squirrels in Kluane, Yukon.

  • A red squirrel in Kluane, Yukon, one of the individuals in the study population.

For my Master’s project, I was interested in red squirrel territorial behavior and the vocalizations, known as rattles, used to defend their territories. Red squirrel rattles are individually unique and have been shown to be used to discriminate kin, though the mechanism underlying this ability is unknown. In a recently published paper in Behavioral Ecology, I sought to distinguish between the mechanisms of ‘prior association’, where animals learn the phenotypes of kin they associate with early in life, and ‘phenotype matching’, where animals use a template to match phenotypes, thereby allowing them to recognize kin without an association early in life. I recorded rattles from squirrels in the field, and used those recordings in playback trials to measure the behavioural responses of squirrels to rattles from familiar kin, unfamiliar kin, and non-kin. One of the major benefits of the Kluane Red Squirrel project is that there is pedigree information for each squirrel, which means that we know who their mother and father is and who their siblings are. Without this information, this project would not have been possible, and full pedigree information is difficult to obtain for wild populations of animals.

  • Recording rattles from squirrels in the field to use in the playback trials

For red squirrels, familiar kin consisted of pair of squirrels that shared a natal nest (e.g. mother-offspring pairs and siblings from the same litter), and unfamiliar kin consisted of pairs of squirrels that did not share a natal nest (e.g. father-offspring pairs, siblings from different litters). Initial analyses revealed that red squirrels did not discriminate between familiar and unfamiliar kin, but also did not discriminate between kin and non-kin, despite previous evidence indicating this capability. Post-hoc analyses showed that a squirrel’s propensity to rattle in response to playback depended on an interaction between relatedness and how the playback stimuli had been recorded. Rattles used as the playback stimuli were either recorded from squirrels as they moved freely around their territories (unsolicited), or from squirrels as they were released from a trap or in response to a broadcast rattle (provoked). Red squirrels discriminated between rattles from close kin (relatedness coefficient of at least 0.5) and rattles from less related kin or non-kin (relatedness coefficient of less than 0.5) when the rattles were recorded from provoked squirrels. Squirrels did not exhibit kin discrimination in response to rattles that had been recorded from unprovoked squirrels.

This figure show the probability of a rattle response from the subject squirrel during the playback period by relatedness coefficient calculated from the pedigree and the collection method of obtaining the rattle stimulus. Unsolicited rattles were recorded from squirrels moving freely around their territories (n = 67 trials), and provoked rattles (n = 38 trials) were recorded from squirrels as they emerged from a live-trap or from squirrels responding to a rattle playback

This is potentially quite interesting, but it is important to note that this relationship was identified through exploratory post hoc analyses and needs to be tested more rigorously. If these results are robust, however, they would suggest that a squirrel’s physiological state might influence the structure of its rattles, including those individually distinctive structural features that are presumably used in discrimination. This raises interesting questions about what kind of information may be contained in the rattles and suggests that rattles may reflect the current state of stress or aggressiveness of the squirrel.

Photos and post by Julia Shonfield

Julia Shonfield, Jamieson C. Gorrell, David W. Coltman, Stan Boutin, Murray M. Humphries, David R. Wilson, Andrew G. McAdam. 2016. Using playback of territorial calls to investigate mechanisms of kin discrimination in red squirrels. Behavioral Ecology arw165. doi: 10.1093/beheco/arw165.

The abstract and a link to the full text can be found here:

If you are unable to access the article but are interested in reading it, you can email me at julia.shonfield@gmail.com and I can provide you with a copy.

 

 

 

 

Thesis Defence Seminar on Red Squirrels

As part of her PhD thesis defense, Wild49 member Jessica Haines will be presenting a one-hour public seminar at 1pm on January 12, 2017, in room CCIS 1-243 at the University of Alberta. Her talk title and abstract are below.


Resources and Reproductive Trade-offs Affect Fitness, Life History Traits, and Sexual Selection in Red Squirrels
Animals face trade-offs throughout life between competing functions, such as between self-maintenance, reproduction, and survival. Resource allocation between these competing functions leads to different patterns of life history traits, changes in investment in reproductive effort, and different patterns of reproductive success. Reproductive investment is also influenced by the environment, for example by resource availability or mating opportunities. In this thesis, I test for evidence of reproductive and life history trade-offs, as well as for whether individual- and population-level resource availability affect reproduction and life history traits. I first tested whether there was evidence of age-related changes in reproductive success in male red squirrels, and in particular whether there was evidence of senescent decline in older ages. I also considered whether there was a trade-off between early-life reproduction and late-life senescence in male red squirrels. Next, I tested whether encountering a resource pulse affected life history traits. I also explored whether life history trade-offs and the fitness consequences of life history traits were affected by encountering a resource pulse called a mast year. Finally, I tested whether individual-level food availability was related with breeding season timing and reproductive success in male and female red squirrels.

 

Field Fun Friday

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Second year male in 2015 with a light, indistinct necklace.

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The same male captured in 2016, now an after second year male with a bold, distinct necklace.

During the breeding season, male songbirds often have brightly coloured and contrasting feather patterns to attract females. These patterns often become more pronounced and defined in older adult males. One of the distinguishing features of the Canada Warbler is the adult male’s dark necklaced feather pattern, which gets darker and more distinct after their second year. Not only did our banded male from 2015 return to the same breeding location, but he came back in 2016 sporting a beautifully developed necklace, and was accompanied by a nesting female! Looks like a year abroad did wonders for this warbler’s appeal. Post and photos by Anjolene Hunt.

Field Fun Friday

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It’s always fun to change things up and work with a new species or in a new habitat. Songbird researcher Anjolene Hunt was happy to help Jesse Watson, Frank Pouw, and Walter the owl carry out Broad-winged hawk capture and transmitter attachment as part of the Migratory Connectivity Project, a collaborative effort between the Smithsonian Migratory Bird Center and the University of Alberta. Photos and post by Anjolene Hunt.

Public Outreach: Wetland Ecosystems Talk at St. Edmund Elementary/ Junior High School

Last week, Logan McLeod and myself travelled to St. Edmund Elementary/ Junior High School to give a presentation on wetland ecosystems to the grade 5 students. The students learned about wetlands, including the differences between wetland classes and what kinds of flora and fauna can be found in these habitats. We also introduced the students to our work with bioacoustics and had them identify some of the vocalizations of common wetland species. The talk ended in a brief meet and greet with three tiger salamanders, which we had brought along to show the students. The students took in a huge amount of information on wetland ecosystems and left the presentation ready to go explore the local wetlands in our city. One step to conserving our wetlands is understanding their value by experiencing them first hand.

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Text by Natasha Annich, photos by Christina Panizzon, grade 5 teacher at St. Edmund Elementary/Junior High school.

An Ode to the Boreal Forest

This week, PhD student Julia Shonfield wrote a blog post for Dispatches from the Field about her experience doing field work over multiple seasons in the boreal forest. The boreal forest covers a huge area in Canada, yet many Canadians don’t really know too much about how incredibly varied this ecosystem is or what it’s like to work there. Check it out on Dispatches from the Field. Each week you can tune in to that website to find out what field work is really like.