The massive/tiny scale of ancient DNA


Wild tuco-tuco. Photo by Anand Varma, former member of my lab;

Take a tooth. Leave it in a cave for 5000 years. Retrieve it and examine the tooth: after all that time, those seasons passing and bacteria working away, what is left of the original animal? Not a lot; but not nothing.

There remains still some DNA from the original owner of the tooth, but degraded, fragmented into little pieces, and overwhelmingly outnumbered by the DNA of all the bacteria that have grown and reproduced and died in the tooth. Finding the DNA of the original animal would be like finding a needle in a haystack—if the haystack was really big and the needle was also a piece of hay, just slightly different from all the other hay.

And yet: we can do it.

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A new, fuzzier project



But I’m now also generating data on tuco-tucos.


The noble tuco-tuco, a subterranean South American rodent.

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What can we learn from 1500 junco bills?






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House Wrens are complicated, mysterious cheaters


I got my start in ornithology studying the love lives of House Wrens. House Wrens pair up to raise their babies in a manner compellingly analogous to the human “nuclear family;” but, like most birds, both partners also often “cheat” on each other (i.e., copulate with other birds). This means that the male wren may have chicks in other nests besides his own, and he may end up caring for chicks that are not biologically related to him. (Note: edited. The original version of this sentence had a mistake.)

This sets up a number of interesting questions, such as: why cheat on your partner? Are the chicks sired by outside birds somehow better? Do males know when they are caring for chicks who aren’t their own? The answer to the latter question seems pretty clear (no, the males do not know), but the former two are more challenging.

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The very confused wren and the birdwatcher who noticed

In the spring of 2015, a male House Wren and his mate built their nest inside a nestbox near a honeysuckle. His mate laid her eggs and dutifully incubated them. Then, one morning— cheep! cheep! High-pitched calls and gaping red mouths cried hungry, daddy! and the male wren was off in a paternal tizzy, collecting bugs and delivering them to his new offspring.

It was, maybe, odd that his new offspring weren’t in the nest that he had built. It was, maybe, odd that other, larger birds were also feeding his babies. It might even have been called odd that his mate was still sitting in their nest, atop whole and silent eggs. But— cheep! No time for that! The chicks were hungry!

What this male House Wren was doing, no doubt to the profound irritation of his mate, was feeding the offspring of a pair of Northern Cardinals who had nested in the honeysuckle near his nestbox.

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Hurray for California rain

California is in the middle of a severe drought. Winter is the rainy season here, and the last two winters weren’t rainy. The drought’s major human impact has been agriculture-related: California grows a hefty portion of the US’s fruits, vegetables, and livestock, all of which require water. The drive to my field sites takes me through the agriculture-heavy Central Valley, and the drought was clearly apparent this summer. The fields were all cracked dry earth and yellow grass, with the rare irrigated green square standing out like artificial turf. One afternoon late in the field season, a light rain sprinkled as we drove through the valley, and we rolled down the windows and cheered.

The Central Valley is thirsty.

The Central Valley is thirsty.

Concerns over agriculture affect everyone; but beyond them, and more personally, I can’t help seeing the drought through the lens of a field biologist.

I have colleagues who slip and slosh through mud all summer to study Black Rails—or who hope that there will be mud to slosh through, anyway, because the small, secretive Black Rail relies on the existence of marshes in which to hide from predators and hatch its comically large-footed chicks. Less rain means fewer and smaller marshes for the Black Rails.

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