New article in Proceedings B! Litter sex ratios in red squirrels

I am very excited to announce our new paper is out in Proceedings of the Royal Society B: Biological Sciences!

Wishart AE, Williams CT, McAdam AG, Boutin S, Dantzer B, Humphries MM, Coltman DW, Lane JE (2018) Is biasing offspring sex ratio adaptive? A test of Fisher’s principle across multiple generations of a wild mammal in a fluctuating environment. Proceedings of the Royal Society B: Biological Sciences 285(1891):


This paper means a lot to me for a few reasons, beyond the value of the reults. One, it’s my first ever first-author paper, and I’m so pleased for it to be in my beloved Kluane Red Squirrel Project study system with this team. Two, I learned so, so much about our data, R, and models in general. Three: it has its roots in some good old fashioned field musings!

During my first field season in 2016 in the Yukon working with red squirrels, I was on the spring nest team where we follow female pregnancies and try to pinpoint the exact date that each female gives birth to her pups. This means lots of telemetry, lots of snowshoeing, lots of tree climbing, but also the amazing experience of holding lots of day-old (and sometimes younger!) baby squirrels. When we find the nests, we count how many pups there are of each sex. It started to seem like many of the nests we were doing in one area had lots of litters of 2 males, 1 female, but that certainly wasn’t the rule and we did see a lot of variation around that. Sitting around in the cookshack, we started asking whether that was typical for red squirrels. And, what was the adult sex ratio of red squirrels anyways? We are lucky in the Kluane Red Squirrel Project to have a fully-enumerated population that we can ask these questions in. And even better, this project has been running for decades, meaning I could dive into the long-term records to find an answer over many, many years.

Of course, once one starts wading into the literature on sex ratio theory, one realizes that there is a huge body of work that already exists. While the reading list grew, it also sparked much more interesting, in-depth, and broadly interesting questions beyond a simple species-specific wondering. My coauthor, Dr Cory T Williams, who had been a post-doc on the project before I started and is now a professor at the University of Alaska in Fairbanks, had started asking some similar questions about litter sex ratios in red squirrels himself, and so we got in touch and I began to build off the analyses he had already began. The valuable data, ideas, comments, and encouragement from the all of the authors helped immensely to make the manuscript a reality.

Given that the early ideas were born in the boreal forest of the southwest Yukon, it was fitting that I was in the field again when it came time to tackle reviewer comments (which were, to note, not only fair but incredibly constructive and immensely professional – this is the peer review environment I dream of). I managed to upload everything while sitting in our beloved pickup truck Ruby parked next to a ditch along the Alaska Highway – complete with dodgy internet signal, way too little sleep, way too much coffee, and all my current fieldwork on the brain. I had visits from both a moose and a great horned owl, the latter simply stared at me with big eyes and little sympathy while I pulled my hair out over another lost connection. But in the end, it was totally worth it.

I hope you get a chance to look at our paper! If you attended either Wildlife 70 in Peterborough, ON or CSEE 2017 in Victoria, BC, you might have caught the early versions of this work. With all the R scripting and model busting that goes into this kind of project, it is so cool to remember that it all originates from observing a few nests of newborn squirrels in the quiet wilderness of the Yukon. The photo is of me in the field gathering data about a litter (weighing & sexing) before we carefully replaced the pups back with mom, who will raise the these little naked darlings up to become beautiful, chattery red squirrels. •

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