Sunday, 18 November 2018
Sunday, 11 November 2018
An obvious example are alarm calls, in which one member of a herd or other group will alert its fellows of a predator or other threat. Another are the distressed 'separation calls' that young mammals use when they can' find their mother. And then, of course, there are mating calls, or aggressive roars and the like intended to intimidate a rival.
But there are also peaceful, non-sexual, contact calls whose primary intent appears to be simply maintaining the cohesion of the group. For example, meerkats regularly use calls to decide when to move on to new foraging grounds, keeping the group together using the principle that if three or more members 'vote' to move by making the appropriate call, then everybody moves at once. African elephants can even use long-distance communication to maintain social bonds with individuals that may be literally miles away.
Sunday, 4 November 2018
|Kubanochoerus, the unicorn-pig|
Indeed, in some respects, the pig family as it exists today is a shadow of its former self. Pigs have always been reasonably successful animals (at least, without human interference), given their adaptability, moderate intelligence, and willingness to eat just about anything. But, in the past, they were more varied than today. In total, there are five generally recognised subfamilies within the overarching pig family - and all but one of them are known only from fossils.
Sunday, 28 October 2018
As the climate warmed, sea levels rose, flooding low-lying coastal regions and turning major valleys into bays. For much of the epoch, for instance, Florida was almost entirely underwater. Further north, however, it was still connected to Asia (and Greenland, although that's less significant in the grand scheme of things). Perhaps because the land bridge was both far to the north and relatively mountainous, not many animals seem to have crossed it, but that changed in the Early Miocene as the climate began to improve, and only increased as the epoch wore on. And, for whatever reason, most of them were heading east - into America.
Sunday, 21 October 2018
It may also not matter too much if the animal lives somewhere where the seasons don't change too much, although, even in the tropics, where there's no winter, there's usually a rainy and a dry season. A great many mammals, however, do have a specific breeding season, timed to be one gestation-length away from the best time to give birth. If pregnancy lasts six months, and the best time to give birth is in the spring, when fresh plants are sprouting, you'd better do your mating in the autumn. If pregnancy lasts twelve months, however, you want to mate in the spring. And so on.
Sunday, 14 October 2018
|Greater bulldog bat|
One of the more unlikey food sources, however, is fish. Yet, when you think about it, fish is a really common food source for birds - there are a huge number of bird species that feed primarily on fish, including seagulls, kingfishers, and ospreys, among many others. Clearly, there's no inherent reason why a flying mammal couldn't eat fish, yet very few of them do.
As a recent review makes clear, however, "very few" is not "none".
Sunday, 7 October 2018
The peccary family is, however, a lot smaller than the pig family: it contains just three living species.
The one that's likely most familiar to readers of this blog is also the most widespread: the collared peccary (Pecari tajacu). It's so-named because of the thin 'collar' of whitish hair that runs from its shoulders across the throat, although, in practice, this isn't always as visible as it might be. The animal is found through pretty much the whole of central and northern South America east of the Andes, through most of Central America, coastal (but not central) regions of Mexico, and into neighbouring parts of the USA, where it can be seen in Arizona, New Mexico, and Texas. If a distinction is needed, this is the true "javelina", since it's the one that's common where that alternative word for "peccary" is most commonly used.