Antlers and Ageing

Ageing is an inevitable fact of life. Without it, populations would rapidly expand to the point that insufficient resources existed to maintain them, unless we also do away with reproduction. And, if we do that, then the creature in question will never be very numerous, and will be wiped out by the first accident, natural disaster, or change in climate conditions to come along. This is something that has been the case since well before mammals existed, even if the nature and pace of ageing might be different for, say, an oak tree or a coral colony, or conceptually vague, as in a mycelial network.

When it comes to reproductive senescence, however, there is a difference in the way this affects male and female mammals. Females are born with a finite supply of eggs, although, in practice, this is far more than they will need, so they don't cease to be fertile simply because they run out. What actually triggers the menopause in humans is complex, even assuming no confounding health conditions, but the number of remaining egg follicles falling below a required level and thereby lowering the production of certain hormones is thought to be key.

All the World's Deer: Deer With Spots

Fallow deer

The fawns of most (but not all) deer species are born with spotted coats, which likely help to camouflage them among the dappled light of a forest. In some species, the spots disappear shortly after birth, while others retain them for a while longer. In five species, however, they keep them all the way into adulthood. I've covered two of these species already: the sika deer of Japan and the um... spotted deer of the Philippines. 

To Europeans, however, the best-known is surely the fallow deer (Dama dama). This is Europe's medium-sized deer, and one of the six original species of deer identified as such in the first list of scientific names in 1758. It lives in woodland areas across most of western and central Europe, preferring broadleaf forests but happy enough with conifers or Mediterranean scrubland. They don't like deep snow, and so aren't found in the Alps or all but the most southerly parts of Scandinavia, but otherwise, they seem pretty adaptable and widespread. Yet, despite being such a familiar animal, they're arguably not really native to the continent.