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Caleb Krueger

@cheloevo

PhD student at Michigan State’s Kellogg Biological Station researching spotted turtle phylogeography and the evolution of temperature-dependent sex determination

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26.01.2025
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Latest posts by Caleb Krueger @cheloevo

That ice is THICK!

21.02.2026 22:33 👍 2 🔁 0 💬 1 📌 0

So I did something a bit different :). Thrilled to see this fun project out! 🐟 #genomics

"Female-biased sex ratios despite stable genetic sex determination across a climatic gradient in a marine fish"

www.biorxiv.org/content/10.6...

18.02.2026 08:31 👍 14 🔁 6 💬 1 📌 0
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ROSIE, a database of reptilian offspring sex ratios and sex-determining mechanisms, beginning with Testudines - Scientific Data Measurement(s) sex-determining mechanism • offspring sex ratio • sex determination • incubation environment Technology Type(s) systematic review study design Sample Characteristic - Organism...

I’m continuing to compile this type of reptile sex determination data in an unreleased version of the ROSIE database. I’ll publish the full thing eventually (2027?), but until then, let me know if it could be useful to you. Here’s the initial, turtle-only version:

www.nature.com/articles/s41...

05.02.2026 18:42 👍 0 🔁 0 💬 0 📌 0
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Exploring the stability of sex chromosome systems in Anolis and other iguanas Abstract. Sex determination was once thought to be unstable in ectothermic vertebrates, but several highly diversified groups of non-avian reptiles, such a

Oh boy, sex-determining mechanisms for a few dozen reptile species just dropped! It feels like getting a present when folks publish data like this.

Looks like sex chromosome systems have been described for almost 100 anole species now!

academic.oup.com/evolut/artic...

05.02.2026 18:42 👍 1 🔁 0 💬 1 📌 0

New preprint!! 🚨 Did you know that many vertebrate species determine sex based on environmental conditions rather than chromosomes? Some turtles, like Trachemys scripta, rely on temperature. We learned more about how this happen molecularly.👇
www.biorxiv.org/content/10.6...

02.02.2026 11:18 👍 20 🔁 13 💬 1 📌 3

🗣️ “Texas is hot, I can be cold” 🔥

16.01.2026 17:18 👍 1 🔁 0 💬 0 📌 0
A summer view of KBS's Windmill Island, showing the island's windmill and footbridge, with Gull Lake in the background.

A summer view of KBS's Windmill Island, showing the island's windmill and footbridge, with Gull Lake in the background.

Join us in congratulating the students, staff and faculty who garnered accolades for their excellent work from July 2024 through June 2025: bit.ly/4pUmdiR

30.12.2025 18:03 👍 5 🔁 1 💬 0 📌 0
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Archaeological evidence of intensive indigenous farming in Michigan’s Upper Peninsula, USA We describe archaeological evidence of intensive ancestral Native American agriculture in the now heavily forested Upper Peninsula of Michigan. Recent LIDAR (light detection and ranging) and excavatio...

A study in Science reveals an extensive precolonial agricultural landscape in Michigan’s Upper Peninsula, suggesting Indigenous American communities cultivated maize intensively between 1000 and 1600 CE, despite a cold climate and marginal growing conditions. https://scim.ag/49voBGO

30.12.2025 20:28 👍 112 🔁 35 💬 0 📌 2

We’ve started the Thermal
Ecology Alliance! Go grab a cup of TEA and join the movement www.thermalecologyalliance.org/participation

26.11.2025 09:31 👍 17 🔁 8 💬 1 📌 0
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Graduate students, have you heard the news? The Orianne Society’s Grant Program for Reptile and Amphibian Conservation in the Southeast is now accepting applications!

Application deadline: 5PM EST, 21 November 2025

Scan QR code or follow link for details: www.oriannesociety.org/science-init...

23.10.2025 14:47 👍 7 🔁 4 💬 0 📌 0
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Dr. Jenkins sits down with Drs. Eric Hileman and Meaghan Clark for an in-depth look at the Eastern Massasauga. Their studies reveal concerning levels of inbreeding, which are linked to reduced survival and lower breeding rates.

11.10.2025 13:07 👍 6 🔁 4 💬 1 📌 0

Now out in the September issue of @journal-evo.bsky.social!

- Pop-level thresholds between male/female development (Tpiv) correlate with mean incubation temps among species, but temp variability within species

- Threshold variation within pops (TRT) is more complex and confounded by study design

08.10.2025 15:52 👍 9 🔁 5 💬 0 📌 0
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Attention graduate students! The Orianne Society’s Grant Program for Reptile and Amphibian Conservation in the Southeast is now accepting applications.

Application deadline: 5PM EST, 21 November 2025

Scan QR code or follow this link for details: www.oriannesociety.org/science-init...

07.10.2025 16:23 👍 5 🔁 1 💬 0 📌 0
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Anatomical and histological analysis of an undescribed cervical skin fold structure in spotted turtles (Clemmys gutatta) - Scientific Reports Turtles evolved over 230 million years ago during the Triassic period, and are a group of ectothermic reptiles that can be found everywhere in the world except Antarctica. There are approximately...

Despite how often I’ve had a spotted turtle retract its head and thought “Wow, that thing is really tucked away!”, I somehow don’t have a picture of it to share. But apparently that neck skin has evolved to be thick and protective and now it has a name: the clemmysian fold!

doi.org/10.1038/s415...

13.08.2025 14:36 👍 13 🔁 3 💬 0 📌 0
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A wee thing helped across the road today. I think this is the smallest wild box turtle I’ve ever seen - just hatched last fall!

10.08.2025 20:37 👍 0 🔁 0 💬 0 📌 0
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Haven’t practiced photography in a while, but Mooney was a cooperative enough model while I quickly reminded myself how a flash works

03.08.2025 00:33 👍 0 🔁 0 💬 0 📌 0
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Hey #JMIH2025, interested in temperature-dependent sex determination? Come to my talk at 1:30 today, right at the beginning of session 18!

11.07.2025 13:17 👍 1 🔁 0 💬 0 📌 0
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The tortoise and the air: climate shapes sex-ratio reaction norm variation in turtles Abstract. For some species, gonadal sex determination relies on environmental cues and thus ought to match local conditions, which can be accomplished thro

Proofs are up for my latest pub in @journal-evo.bsky.social! It’s a big ol’ analysis of how sex-ratio reaction norms vary with local climates within and among turtle species with TSD. Check it out here:

doi.org/10.1093/evol...

26.06.2025 17:41 👍 8 🔁 6 💬 0 📌 1
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Nothing hits quite like finding a new population of these guys

30.05.2025 01:04 👍 2 🔁 0 💬 0 📌 0
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The duality of turtles

15.05.2025 00:04 👍 1 🔁 0 💬 0 📌 0

I’ve only played a small role, but I’m excited to be a part of the revamped Tree of Sex group and to see what’s coming!

13.05.2025 12:05 👍 1 🔁 0 💬 0 📌 0
4 12x18 inch posters on a brick and concrete wall. The top left is pink and says funding science saves lives, written in microbes, next to a microscope. The one on the right says Biology is bigger than binaries, with a fish, a lily, and a bee. The bottom left says Protecting wildlife starts wtih you, with a bunch of adiorable woodland creatues in yellow, white and black, including an owl, fungi, a... um. weasel? salamanders, butterflies, slugs, and a rotting log. The bottom right says Will our oceans thrive or nosedive the choice is yours, with the ocean represented in a circle, half of which is dead and half of which is alive, including kelp and a mackerel

4 12x18 inch posters on a brick and concrete wall. The top left is pink and says funding science saves lives, written in microbes, next to a microscope. The one on the right says Biology is bigger than binaries, with a fish, a lily, and a bee. The bottom left says Protecting wildlife starts wtih you, with a bunch of adiorable woodland creatues in yellow, white and black, including an owl, fungi, a... um. weasel? salamanders, butterflies, slugs, and a rotting log. The bottom right says Will our oceans thrive or nosedive the choice is yours, with the ocean represented in a circle, half of which is dead and half of which is alive, including kelp and a mackerel

🚨 Cool new project alert 🚨

WE- you, me, everyone- need to work together to get important science messages out to people.

4 artists & 3 scientists collab'd on these posters. We hope YOU will put them out in your community. Each poster comes w/info about each topic.

Get 'em Squidfacts.bigcartel.com

06.05.2025 14:26 👍 5319 🔁 1736 💬 98 📌 74
Scatter plot showing a negative relationship between tree canopy cover over painted turtle nest sites and head emergence latency (a measure of boldness) in a novel arena behavior assay.

Scatter plot showing a negative relationship between tree canopy cover over painted turtle nest sites and head emergence latency (a measure of boldness) in a novel arena behavior assay.

New research from our lab exploring the ecological consequences of behavioral syndromes! @morganichemistry.bsky.social shows that antipredator behavior in painted turtles is repeatable and associated with ecologically significant variation in nest site choice.
authors.elsevier.com/c/1k-tHmjMA3pk

28.04.2025 19:18 👍 4 🔁 2 💬 0 📌 0
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a woman talking on a cell phone with the words " i 'd like to offer you a job " below her ALT: a woman talking on a cell phone with the words " i 'd like to offer you a job " below her

Crazy times, but I'll be advertising for a 2 year postdoc to work with me on new comp. methods to estimate evolutionary history soon - specifically to develop methods to handle missing data (e.g. ascertainment bias, allele dropout). Are you a comp. biologist graduating with a PhD soon? Reach out!

28.04.2025 20:24 👍 39 🔁 31 💬 0 📌 0
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We’ve reached new records of small in the field recently

28.04.2025 14:29 👍 1 🔁 0 💬 0 📌 0
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One of the biggest and one of the smallest Blanding’s I’ve caught so far! The big one has about 2 decades on the small one

24.04.2025 21:54 👍 0 🔁 0 💬 0 📌 0
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Bumper day for Blanding’s

20.04.2025 22:55 👍 0 🔁 0 💬 0 📌 0
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19.04.2025 20:41 👍 0 🔁 0 💬 0 📌 0
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Today was for 20+ year old Blanding’s

19.04.2025 20:40 👍 0 🔁 0 💬 1 📌 0
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I know it’s field season when my camera roll starts to look like this:

13.04.2025 22:37 👍 0 🔁 0 💬 0 📌 0