unprecedented acorn abundance: anomaly or illusion?

November 14, 2019 2:34 PM

I live in a Brooklyn neighborhood with a lot of oak trees, and it feels like this autumn there have been waaaaay more acorns than in any of the 20 previous autumns I've been around here. Can any Northeastern US naturalists confirm it's been a big acorn season this year and maybe explain why?
posted by moonmilk to Science & Nature (13 answers total)

Best answer: The googleable term is mast year, this article might help. In short, yes this has been a big year.
posted by jessamyn at 2:37 PM on November 14, 2019 [9 favorites]

I'm in the northeast and there are so many acorns we're slipping on them in the yard. It's genuinely difficult to walk, and it's not that we don't clean up.

It's a mast year.

Weirdly, I'm not seeing that many squirrels but I think they might be hunkering down to produce a winter litter of pups to skitter across the street in a few weeks, so maybe that's why it's quiet on the squirrel front.
posted by A Terrible Llama at 2:56 PM on November 14, 2019

Best answer: It's a mast year, all across the region! My sense is that it's mostly red oaks masting and that white oaks are down, but I don't know if that's true everywhere.
posted by pemberkins at 3:09 PM on November 14, 2019 [3 favorites]

Response by poster: I don’t know how to tell the different oaks apart, but the tiny round acorns, medium round acorns, and huge elongated acorns are all abundant this year in Brooklyn. I enjoy stomping on them while walking the dog.
posted by moonmilk at 3:29 PM on November 14, 2019 [4 favorites]

If you're interested in figuring the different oaks out, here are some great reference images for different species' acorns (and leaves, and bark, and twigs...)
posted by pemberkins at 3:53 PM on November 14, 2019 [1 favorite]

Mast years followed by years of dearth seem likely to have something to do with the very unusual lifespans of squirrels, which can live up to at least 23 years, the longest among rodents, which make up about 40% of all species of mammals.

I've never been able to find a source claiming that years of mast tend to have fixed intervals like the 13 and 17 years of cicada booms, which apparently are primes to optimize the predator evasion effectiveness of long intervals between big populations.
posted by jamjam at 4:26 PM on November 14, 2019 [2 favorites]

Response by poster: The article that jessamyn linked says that mast years lead to a mouse boom the next year, which leads to a tick boom, which leads to a disease-infected-tick boom the year after that! Ughhhhh.
posted by moonmilk at 4:32 PM on November 14, 2019

Definitely wide swings in amounts. I wrote this about the last super-acorn year...
posted by notsnot at 4:46 PM on November 14, 2019

It's been a really big year for walnuts and maple keys and just about everything here in Southern Ontario I think it's because of the long, wet, winter and spring.
posted by Enid Lareg at 4:53 PM on November 14, 2019 [1 favorite]

In case it's of interest - the forests orangutans live in are also dominated by masting trees and that's part of why they have such long childhoods and long lifespans! At least in Indonesia, masting is very unpredictable.
posted by ChuraChura at 6:13 PM on November 14, 2019 [1 favorite]

If you want to dig further into *why* nature decided that a mast year makes sense, I can't recommend the book Braiding Sweetgrass enough!
posted by jeremias at 7:21 PM on November 14, 2019 [1 favorite]

Response by poster: I did read Braiding Sweetgrass and apparently it didn't stick...
posted by moonmilk at 7:30 PM on November 14, 2019

Also possibly of interest, the year following a mast year is usually a population boom for ticks (and the associated lyme disease) so tuck your pants in your shoes and all that.
posted by gloriouslyincandescent at 5:40 PM on November 15, 2019 [1 favorite]