Cows & Climate

Fruits trees and flowers aren’t the only organisms doing it. Turns out some cows are also breeding on a different schedule due to a shifting climate. An iconic British cattle breed is conceiving young earlier in the spring due to warmer temperatures, a new study finds. But that means some calves are born in winter, and have a lower chance of surviving.

Chillingham cattle, which have distinctive white coats, red ears and horns, are a rare ancient breed. Since at least the early 1600s, they have been feral. Today, a small herd runs wild over pastures on a large estate in Northumberland in the northern United Kingdom (UK). Estate managers have kept records on cattle births and deaths since the 1860s, giving scientists an unusually long-term dataset they could use to study cattle “phenology” – the timing of key biological events.

“The Chillingham cattle data are unique and, as far as we know, the longest mammal phenology dataset in the world,” says Sarah Burthe of the UK’s Centre for Ecology & Hydrology. “It’s an amazing dataset.”

In the Journal of Animal Ecology, Burthe and five colleagues report on an effort to use that dataset to see how the UK shifting climate has affected Chillingham cattle. They found that, over time, the breed – which gives birth throughout the year, unlike most other mammals — was having more calves during the winter. Weather data suggested a reason: warmer springs nine months earlier. “Cattle have a nine-month gestation period,” says Burthe. “Warm springs allow vegetation to start growing earlier, providing the cattle with more nutritious plant growth, and more cows conceive earlier as a result.”

But there is a downside to winter births, she adds. “Winter-born calves don’t do very well and are more likely to die before they reach the age of one. This suggests that the cattle are responding to climate change, but this is having a negative impact on them.”

Still, the results are notable because they suggest that even species able to breed year-round, which might be expected to cope better with environmental change, are altering the timing of their breeding schedules due to changing temperatures. David Malakoff | June 14, 2011

Source: Sarah Burthe et al (2011). Demographic consequences of increased winter births in a large aseasonally breeding mammal (Bos taurus) in response to climate change. Journal of Animal Ecology. DOI: 10.1111/j.1365-2656.2011.01865.x

Image: Copyright Sarah Burthe, courtesy British Ecological Society