Sunday, 28 February 2021
Sunday, 21 February 2021
The dog family has its origins in North America and it seems clear that what happened here is that some wolf-relative that happened to look a bit like a fox headed south at some point, where all of its remaining descendants live today. North and South America joined up relatively recently, geologically speaking, so it's likely that the origins of the South American foxes actually lie in the North, already looking somewhat like their modern form before they made the trip.
Sunday, 14 February 2021
That's common in birds, perhaps in part because they have to physically fetch and deliver food rather than producing milk with the calories from their own diet, not to mention the effort of incubating eggs. But, in mammals, while it certainly occurs in some species (as do the other two options) the most common pattern is polygyny.
Sunday, 7 February 2021
By far the largest are the "murine" or "typical" mice which contains... well, almost everything. According to that particular study, they split from the other members of the mouse family about 18 million years ago, during the Early Miocene. Then, about 16 million years ago, as the Middle Miocene dawned, the remainder split into what are now recognised as two distinct subfamilies: the gerbils and the "deomyine" mice. (The latter look almost exactly like the murine sort, and it took this sort of study to prove that they weren't).
Saturday, 30 January 2021
|Doe (a deer, a female deer)|
Antlers are, of course, the key defining feature of the deer family, the Cervidae. They are found on (almost) every species in the family, although (almost) only on the males. A large stag with branching antlers is instantly identifiable as a deer, but it may be fair to say that some of the species with unbranched antlers do have a certain resemblance to some of the smaller species of antelope.
Sunday, 24 January 2021
The first horses entered Africa towards the end of the Middle Miocene, about 10 million years ago. These have commonly been assigned to the same genera, Hipparion and Hippotherium, as were found in Eurasia at the time, although the fine details of the exact relationships are unclear. Although the latter in particular seems to have been reasonably successful on the continent, a more significant immigration from an African perspective took place later on, around 8 million years ago as the drier climate heralded the start of the Late Miocene.
Sunday, 17 January 2021
In social species, however, the end result is that herds (or other groupings) are united primarily by their female relationships. The females in a herd are likely sisters or other close relatives, while the males have travelled from elsewhere and are not only not closely related to the females, but may not even be closely related to each other, either. Often males spend some time living on their own before they find a suitable herd to join (perhaps because the existing dominant male is getting on a bit) with the result that there's a distinct female-bias in membership of the group.