Lions, New Tigers, and Bears, oh my: The 344th Evolutionary Lens with Bret Weinstein and Heather Heying
September 23, 2026
AI Summary
5 min readIn late June, a bear named Bucky in Alaska's Katmai National Park looked thin and unremarkable. By mid-September, he was enormous—his belly nearly dragging in the water. This transformation is the point of Fat Bear Week, an annual celebration where the public votes on which brown bear has put on the most mass before winter. But the spectacle raises a deeper biological question: why would an animal in a marginal, seasonal habitat evolve to be gigantic rather than tiny?
This episode of the Dark Horse Podcast, with Bret Weinstein and Heather Heying, weaves together three biological stories—a newly discovered cat species, fattening Alaskan bears, and overwhelmed frogs—to explore how evolution solves the problem of survival in patchy, noisy, and resource-limited environments.
A New Cat from the Highlands
A new species of wildcat has been formally described: the Tilkayo (Leopardus tilcayo), a small Bolivian mountain cat weighing about 1.5 to 2 kilograms—smaller than a typical house cat. The discovery began when a local man found an orphaned kitten and raised it for a year before realizing it was not a domestic cat and bringing it to a sanctuary. There, researcher Paula Nogales Ascarrunz recognized it as unusual, and genomic analysis confirmed it is a distinct species, split from its closest relatives for perhaps 1.5 million years.
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What you'll learn
- 1 (00:04) **Seasonal Opening & Episode Preview** - Bret and Heather welcome autumn, define "dehissing" (leaf fall), and preview today's biology topics: cats, bears, and frogs.
- 2 (04:39) **Sponsor Segment: Cowboy Colostrum, Crowd Health, Branch Basics** - Three sponsor reads with product details and discount codes.
- 3 (16:02) **Discovery of the Tilkayo: A New Species of Wildcat** - Introduction to a newly described cat species from Bolivia, named from local knowledge and confirmed by genomics.
- 4 (21:31) **Phylogenetic Context: Feliforms and the Cat Family Tree** - Bret and Heather place the Tilkayo within the broader evolutionary history of cat-like carnivores.
- 5 (34:06) **The Eight Clades of True Cats** - A tour of the major cat lineages, focusing on New World clades and the Tilkayo's place within them.
- 6 (45:06) **The Tilkayo in Detail: Physical Traits, Genomics, and Range** - Deep dive into the paper that established the Tilkayo as a distinct species within the tiger cat complex.
- 7 (54:27) **Why So Many Small Cats? The Ocelot as a Driver of Speciation** - Bret proposes that the larger ocelot creates "cryptic islands" at the edges of its range, allowing smaller tiger cats to evolve.
+ Full timestamped outline available in the app
Guests on this episode
Show Notes
On this, our 344th Evolutionary Lens livestream, we discuss new cats, fat bears, and overwhelmed frogs. The tilcayo, a newly named species of cat from Bolivia, is part of a group of New World “tiger cats” that live on the outskirts of the Amazon basin. We discuss Carnivoran relationships, cats more specifically, and what is known about the history and ecology of the tilcayo in particular. Then: it’s fat bear week at Katmai National Park in Alaska, where grizzlies are fattening themselves on salmon for the Winter ahead; we discuss hibernation, reproductive diapause, and general chonkiness in bears. Finally: female Cope’s gray treefrogs have a harder time choosing good mates when there’s a lot of noise, and when there are too many suitors—kind of like how women often make bad choices when confronted with chaos and wingmen.
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Music: "Marble Machine" by Wintergatan
This track can be downloaded for free at www.wintergatan.net
Free License to use this track in your video can be downloaded at www.wintergatan.net
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Mentioned in this episode:
Lescroart & Nogales-Ascarrunz et al 2026. Phylogenomics and museomics reveal five distinct species of tiger cats in South America. Current Biology 36: 1-15: https://www.cell.com/current-biology/fulltext/S0960-9822(26)01110-3
National Geographic’s tilcayo pics: https://news.nationalgeographic.org/photos-new-wild-cat-species/
Meet the bears: https://explore.org/meet-the-bears#h_75305921118711789688140871
Hemingway et al 2026. Choice overload constrains mate choice independent of energetic masking. iScience 29: 1-13: https://www.cell.com/action/showPdf?pii=S2589-0042%2826%2902464-8
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