Content Warning: heavy discussion of death, decomposition, and impolite body functions.

I believe it was Imhotep in 1999's The Mummy who said "Death is only the beginning...", and he was right! Not in the sense of returning from the realm of the dead to fight Brendan Fraser, but in the sense that death turns an organism's mortal shell into a entirely new sort of ecosystem. In this grisly-yet-surprisingly-positive episode, Nicole walks us through the science of decomposition, how it's applied to everything from solving crimes to food freshness, and why we couldn't live in a world without decay.

Nicole's Sources:

• LET THINGS ROT (the YouTube video Nicole was talking about): https://www.youtube.com/watch?v=PI_-eUOgqFI
• Australian Museum. 2025. Stages of decomposition. CW: pictures of decomposing pigs.
• Matuszewski, S. 2021. Post-Mortem Interval Estimation Based on Insect Evidence: Current Challenges. National Library of Medicine.
• Nowakowski, K. 2025. These beetles eat rotting flesh—and could unlock the next generation of antibiotics. National Geographic.
• Australia's Defining Moments: Digital Classroom. Can we solve the poo problem?

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Content Warning: descriptions of sexual acts and genitalia

Allan's Sources:

1. Coming soon!

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Content Warning: none

In this month's Filthy Animals, Rachel tests the strength of monogamous bonds in the animal kingdom by seeing what the data says about their infidelity. As it turns out, even in species where pair bonds are key to the social survival of the animals, reckless passion can play a big role in their breeding systems. Our host graciously brings us examples ranging from the expected (cuckoos, the species that gives us the word "cuckold") to the obscure (carrion beetles, whose relationship drama plays out in carcasses the world over).

Rachel's Sources:

•  Wysocki, D., et al (2023). Low level of extra-pair paternity in an urban population of blackbirds. The European Zoological Journal, 90(1), 307–312. https://doi.org/10.1080/24750263.2023.2193433

• Gao, L.-F., Zhang, H.-Y., Zhang, W., Sun, Y.-H., Liang, M.-J. and Du, B. (2020), Effects of extra-pair paternity and maternity on the provisioning strategies of the Azure-winged Magpie Cyanopica cyanus. Ibis, 162: 627-636. https://doi.org/10.1111/ibi.12800

• Li M-H, Välimäki K, Piha M, Pakkala T, Merilä J (2009) Extrapair Paternity and Maternity in the Three-Toed Woodpecker, Picoides tridactylus: Insights from Microsatellite-Based Parentage Analysis. PLoS ONE 4(11): e7895. https://doi.org/10.1371/journal.pone.0007895

• Niida, T., Yao, I., Nisimura, T. & Suzuki, S. (2024) Detection of extra-pair maternity in a carrion beetle under natural conditions. Ecological Entomology, 49(5), 734–738. Available from: https://doi.org/10.1111/een.13334

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Content Warning: Discussion of cancer and related illnesses

Cancer is scary. A transmissible, STI-based cancer is even scarier. Canine Transmissible Venereal Tumor (CTVT) is the oldest, most prolific, cancer known in nature. And it's not alone. Nicole illustrates this bizarre disease which is expanding our understanding of cancer itself, and may have given one particular animal the key to immortality.

Nicole's Sources:

• Murchison, E., et al. 2014. Transmissible Dog Cancer Genome Reveals the Origin and History of an Ancient Cell Lineage. Science.
• Gori, K., et al. 2025. Horizontal transfer of nuclear DNA in transmissible cancer. PNAS.
• About Tasmanian devil facial tumor disease. Dept of Natural Resources and Environment Tasmania.
• Bruzos, A. 2022. Heterogeneity of cockle transmissible cancers. YouTube.
• Brain Bleach: Correia-Caeiro, C., Guo, K., Mills, D. 2020. Perception of dynamic facial expressions of emotion between dogs and humans. Animal Cognition.
• Hank Green. The Truth About the Single-Celled Dog. SciShow. YouTube.

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Content Warning: This is a pretty wholesome episode. No fear, dear listener!

In honor of Pride Month, Rachel is taking us beneath the waves and beyond the binary into the fascinatingly queer world of fish! In this episode, she investigates stunningly fluid species that defy the concept of biological sex as an innate and immutable characteristic. SPOILER: Sex and gender in the animal kingdom is far from simple, guys. We should count ourselves lucky to live on such a beautifully un-boring planet. :)

Rachel's Sources:

1. Graves, J., & Todd, E. (2023, January 31). What we learn from fish that change sex. La Trobe University. https://www.latrobe.edu.au/news/articles/2020/opinion/what-we-learn-from-fish-that-change-sex
   1. Actual research: https://doi.org/10.1126/sciadv.aaw7006
2. R. Vega‐Frutis, R. Macías‐Ordóñez, R. Guevara, L. Fromhage, Sex change in plants and animals: a unified perspective, Journal of Evolutionary Biology, Volume 27, Issue 4, 1 April 2014, Pages 667–675, https://doi.org/10.1111/jeb.12333
3. Casas L, Saborido-Rey F. Environmental Cues and Mechanisms Underpinning Sex Change in Fish. Sex Dev. 2021;15(1-3):108-121. doi: 10.1159/000515274. Epub 2021 Jun 10. PMID: 34111868; PMCID: PMC8491468.
4. Munday PL, Buston PM, Warner RR. Diversity and flexibility of sex-change strategies in animals. Trends Ecol Evol. 2006 Feb;21(2):89-95. doi: 10.1016/j.tree.2005.10.020. Epub 2005 Nov 14. PMID: 16701480.

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Content Warning: explicit language, descriptions of sex, pretty wholesome episode honestly

Allan's Sources:

1. Kempenaers, Bart. (2022). Mating systems in birds. Current Biology. 32. R1115-R1121. 10.1016/j.cub.2022.06.066.
2. Kirkpatrick, M., Ryan, M. The evolution of mating preferences and the paradox of the lek. Nature 350, 33–38 (1991). https://doi.org/10.1038/350033a0
3. Rathore A, Isvaran K, Guttal V. 2023 Lekking as collective behaviour. Phil.Trans. R. Soc. B 378: 20220066. https://doi.org/10.1098/rstb.2022.0066

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Content Warning: Drug use, including recreational drugs. Moral panics. Sexual references. Spoiler: ((it's not the cats))

What is catnip, what's its effect on cats, and is it really cats getting horny like so many think? Turns out these answers are a bit more complicated that we first thought.

Nicole's Sources:

1. Shi, X., et al.

Repellency of Novel Catnip Oils Against the Bed Bug (Hemiptera: Cimicidae) | Journal of Medical Entomology.

Oxford Academic.

1. Batume, C., et al. 2024.

Evaluating repellence properties of catnip essential oil against the mosquito species Aedes aegypti using a Y-tube olfactometer

. Scientific Reports.

1. Espín-Iturbe, L., et al. 2017.

Active and passive responses to catnip (Nepeta cataria) are affected by age, sex and early gonadectomy in male and female cats

. Behavioural Processes.

1. Johns Hopkins Medicine. 2019.

Deet Gives Humans an ‘Invisibilty Cloak’ to Fend Off Mosquito Bites

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Content Warning: cannibalism, suicide, coercive/violent sexual behavior, death during pregnancy, partner death, drowning, necrophilia

(start the episode at 36:12 to avoid our discussion of all of the above, which are discussed in the context of "most dangerous courtship behaviors". we promise, it gets much sillier after that!)

Filthy Animals is back! We open Season 2 with some very important data-driven nonsense to settle some burning questions about the world of animal courtship. TO WIT: Which animals are mating in the most dangerous way possible, AND who is doing it the most obnoxiously? Danger and stupidity abound. Let the great debate begin!

Sources: Allan's Sources:

Ancel, A., Gilbert, C. & Beaulieu, M. The long engagement of the emperor penguin. Polar Biol 36, 573–577 (2013). https://doi.org/10.1007/s00300-013-1285-9

Biaggio MD, Sandomirsky I, Lubin Y, Harari AR, Andrade MC. Copulation with immature females increases male fitness in cannibalistic widow spiders. Biol Lett. 2016 Sep;12(9):20160516. doi: 10.1098/rsbl.2016.0516. PMID: 27651535; PMCID: PMC5046930.

Maydianne C. B. Andrade, Risky mate search and male self-sacrifice in redback spiders, Behavioral Ecology, Volume 14, Issue 4, July 2003, Pages 531–538, https://doi.org/10.1093/beheco/arg015

Rachel's Sources: Drop Dead! Female mate avoidance in an explosively breeding frog (2023) https://doi.org/10.1098/rsos.230742

Breeding Mortality in the Wood Frog (2000) https://scholarworks.uark.edu/cgi/viewcontent.cgi?article=1735&context=jaas

Mothers want brainy babies: https://news.cornell.edu/stories/2000/11/female-birds-choose-best-singers-have-smarter-offspring

Birds of the World - Golden-collared Manakin: https://birdsoftheworld.org/bow/species/gocman1/cur/introduction

Nicole's Sources:

Han, C., and Jablonski, P. 2010. Male water striders attract predators to intimidate females into copulation | Nature Communications.

CicadaMania.com

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