Thread by @AlgonquinWRS

The Painted Turtle is one of the most well-studied turtles in the world. What's left to learn? This is a thread about their unexpected love life...

researchgate.net/publication/34…

Now published "Sex, shells, and weaponry", the final research paper from MSc project of Patrick Moldowan

This project took shape from field observations: Ever noticed that Painted Turtles have a "buck-toothed" beak? Why? And why are these "teeth" more variable in size and often larger in males compared to females?

@jr4science + Matt Keevil were instrumental in idea development!

These turtle "teeth" are called #tomiodonts and it turns out that turtles can have one (monocupsid), or two (bicuspid), or three (tricuspid), or none at all!

Learn more about these curious structures here:
researchgate.net/publication/28…

... but why? Do they have a function?

Also while conducting field work, we began to notice that a lot of the turtles had wounds, especially on the head/neck.

Ruling out predators was easy and leeches did not leave these injuries. This prompted another, "why"?

Although most wounds were obscured by scabs and scar tissue, fresh wounds had distinct features:

one or two parallel gashes (red arrows), sometimes with a perpendicular slash.

Yikes! and ouch! ... but odd.

While measuring+weighting a particularly toothy male turtle one day, Patrick was accidentally bitten.

Ouch! The male tomiodonts broke the skin and left little gashes. Eureka💡! Could it be?

📸 The toothy turtle gently restrained in front/side profile + the tell-tale bite wound

Hold up: Everyone knows that the Painted Turtle is the gentleman suitor of the turtle/reptile world!

After all, @cdarwin (1871) wrote: "The male ... has claws on his front feet twice as long as those of the female; and these are used when the sexes unite".

Even Sir David Attenborough @BBCEarth tells us about the courtship of the Painted Turtle. The male's courtship is called titillation and he uses his long front claws to 'tickle' and stroke the female:



All very affectionately amorous, right? Well ...

This set the stage for three questions. Put simply,
- Do tomiodonts differ between the sexes and what is their functional significance?
- How widespread is wounding? Is it sex or size-specific?
- Are the tomiodonts related to the observed wounding? We'd needed behavioural trials!

Here's what Patrick found during his studies:

(1) Tomiodonts of males are much larger than females. These structures may be involved in feeding or maybe breeding (#sexualweaponry?). Tomiodont structure optimizes bite force:

https://twitter.com/AlgonquinWRS/status/786966373721407489

researchgate.net/publication/30…

(2) Head shape is different between the sexes too, and that may have something to do with sexual recognition between individuals and/or performance (e.g., bite force). This is not only statistically demonstrable, but visually obvious to human observers:

researchgate.net/publication/31…

(3) Using 24-years of wounding data from the @AlgonquinWRS turtle study, it was clear that females, especially larger females, disproportionally have wounds.

Are males antagonizing females? Are there courtship and/or coercive reproductive tactics?

researchgate.net/publication/33…

(4) Finally, behavioural trials!

Males shift from courtship->coercive tactics during lifetime and match morphology+behavior!

Small males = prop. long foreclaw ornaments = courtship
Large males = prop. long tomiodonts = coercion

https://twitter.com/AlgonquinWRS/status/1243206605690281994

researchgate.net/publication/34…

Current evidence suggests that tomiodonts are sexual weapons used by larger males in an attempt to coerce females into mating.

Quite shockingly, males engaged in a number of coercive behaviours, including the "shell clattering" seen here (audio on):

(5) Also, Painted Turtles here in the north breed primarily in the late summer and autumn, seemingly unlike more southerly populations. This is of general interest, but may have broader relevance to field sampling (e.g., population studies):

researchgate.net/publication/32…

During his post-grad, Patrick took a roadtrip to #NaturalHistory museums @ROMtoronto, @Cornell, @yalepeabody, @NMNH, @AMNH, @CarnegieMNH, @FloridaMuseum b/c there was something else he wanted to know...

Something curious was going on w/ the turtle shells:

https://twitter.com/AlgonquinWRS/status/925140552752029696

(6) Tomiodonts were not the only weapons! Using museum data, @d_hawkshaw led an outstanding project to show sexual differences in shell shape:

Males have "spiky" shells that are used as weapons too!

researchgate.net/publication/33…

All this to say: There is a still a lot to learn about the common and so-called well-studied species in our own backyards. Invite curiosity, ask questions, challenge yourself and current ways of thinking (with data), and have fun with research.

The research had a Valentine's Day feature by @priyanka_runwal in the @nytimes:

nytimes.com/2020/02/14/sci…

Another major highway of the Painted Turtle weaponry and mating tactics research was getting air time on @herphighlights:

Ep. 64 The Art of Turtle War:
herphighlights.podbean.com/e/064-the-art-…

These projects were supported by long-term turtle studies @AlgonquinWRS, @Algonquin_PP, @OntarioParks, with funding from @NSERC_CRSNG.

Awards from @canuck_herps, @ssarherps, @TurtleSurvival and @RGS_AWS supported this research.

Thanks to dear friends and lab siblings MG Keevil, @jr4science, @salamandertrack, @JamesBG_27, and @PQPTurtles for their friendship, camaraderie, mentorship, and insightful discussions on all subjects tomiodonts and titillation.

Thanks to @AlbrechtS_H and @ESU_LAS_DEAN for constructive feedback during the thesis.

Importantly, thanks to @stevenkell21, @MichAnagnostou, and many many others for help with field work, including long-term data collection on the @AlgonquinWRS turtle project!

Finally, it is with much gratitude that I thank Dr. Jackie Litzgus @LaurentianU. Jackie's open-minded supervising, encouragement, patience+excitement supported a young turtle nerd🐢🤓. She indulged my curiosity+took a chance on a far-fetched project. For that I am truly grateful.