Caribou diet quality triples depending on spring plant timing
Giesen CJ, Hepler J, Karpovich SA, Swingley CS, Barboza PS
Phenology
If you've ever noticed how a late frost delays your garden's first growth spurt, you'll recognize the same timing gamble these caribou face, except their survival and reproduction hinge on catching the exact 14-day window when tundra plants green up.
Researchers followed a herd of female caribou in northern Alaska for three years, checking their poop, blood, and the plants nearby to figure out what they were eating and how healthy they were. They discovered that caribou who showed up at the coast right as spring plants were sprouting ate way better food, protein jumped from 5.6% to over 20%, than caribou who arrived too early or too late. Being in the right place at the right moment during a short two-week green-up window made a real difference in body condition.
Key Findings
Faecal crude protein ranged from 5.6% in 2022 (before green-up, caribou inland) to 20.3% in 2023 (after green-up, caribou near coast)
Serum albumin (4.4 g/dL) and urea nitrogen (9.9 mmol/L) were highest in 2023, matching the high-protein diet period
Isotope data (δ15N, δ13C) showed diets shifted from lichen-dominated to graminoid-dominated depending on green-up timing and caribou location
chevron_right Technical Summary
Scientists tracked wild caribou in Alaska's Arctic and found their diet quality swung wildly depending on whether spring plant growth had started yet, with protein levels ranging from 5.6% to over 20% across three years. Caribou that reached the coast after green-up ate far richer food, which matters for how well females grow and reproduce.
Abstract Preview
Original paper
A migratory herbivore responds to rapid changes in food supply: diet and body condition of an arctic caribou herd at onset of green-up.
Annual migration of ungulates is often correlated with regional and seasonal plant growth, but are smaller scale movements of individuals related to fitness? We investigated the response of wild ca...
open_in_new Read full abstractAbstract copyright held by the original publisher.
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A lichen is a hybrid colony of algae or cyanobacteria living symbiotically among filaments of multiple fungus species, along with bacteria embedded in the cortex, or "skin", in a mutualistic relationship. Lichens are the lifeform that first brought the term symbiosis into biological context.