Eurasian otter © Stephan Morris/iStock
Winter brings many challenges for Eurasian otters. The species has no seasonal fur variation, so expends far more heat and energy swimming and diving in colder waters despite its dense, double-layered coat.
A daily food intake of 15–20 per cent of body weight is key to survival, and otters adapt their patterns of predation and hunting behaviour to make the most of the prey available during these leaner months.
Scottish coastal otters, for example, which usually forage and hunt throughout the day in summer, instead seek prey more intensively in the mornings (though, interestingly, camera-traps set by the International Otter Survival Fund have revealed that they are in fact also active at night).
Winter brings many other dangers to otters. If conditions are mild and wet, cubs can drown in flooded holts. Swollen, murky waters also make swimming more difficult, forcing the animals onto busy roads. You can see why only 50 per cent of youngsters survive to see the spring.
Click here to read more of our Wildlife Q&As.
Do you have a wildlife question you’d like answered? Email your question to firstname.lastname@example.org or post it to Q&A, BBC Wildlife Magazine, Immediate Media Company, 2nd Floor, Tower House, Fairfax Street, Bristol BS1 3BN