Whether or not other mammals menstruate may depend on your exact definition of the term. Chimpanzees certainly do (and, indeed, rarely experience menopause), and it's present to a variable extent in other apes and Old World monkeys. In New World monkeys it's microscopic and it's completely absent in lemurs. At least some bats menstruate, as do sengis (elephant shrews) and, so far as we know, just one species of rodent.
Synapsida
A random wander through the world of mammals
Sunday, 6 April 2025
Of Pregnancy and Progesterone
Saturday, 29 March 2025
The Earliest Landfowl
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Gallinuloides |
The humble chicken (Gallus domesticus) is a member of the pheasant family. This is a moderately-sized family, with around 180 species. Alongside the chicken and its wild ancestor, this also includes, not just pheasants, but many similar ground-dwelling birds, such as grouse, partridges, true quails, turkeys, and peacocks.
It is, in turn, a part of a larger taxonomic group technically referred to as the Galliformes, or more commonly the "landfowl". The other four living families in this order have fewer species and are generally less well-known, but they share the same features of being generally plump, often quite large by avian standards, and having short, rounded wings unsuited for long-distance flight.
Sunday, 23 March 2025
Delphinids: Humpback Dolphins
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Indo-Pacific humpback dolphin |
Our best evidence suggests that it probably isn't a "real" group, in the sense of one consisting of a common ancestor and all of its descendants. That's because three other genera of dolphin appear to be descended from that common ancestor, forming part of the same cluster of what we might describe as "typical-looking" dolphins. The common and bottlenose dolphins form two of these interspersed groups, while the third is represented by the humpback dolphins.
As it turns out, their classification has also had to undergo significant revision in recent years, albeit for different reasons.
Sunday, 16 March 2025
Oligocene (Pt 14): The Southern Horses That Weren't
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Scarritia |
They didn't.
Well, not much. When the name was originally coined, for the Miocene genus Notohippus, back in 1891, it was assumed that they really were horses, or at least closely related. This is because of the shape of their teeth which, did indeed resemble those of equines. It only took until 1914 to realise that, teeth aside, they weren't very horse-like. That their teeth were similar suggests a similar diet with plenty of tough vegetation, and their head was elongated in an almost horse-like fashion to accommodate them... but that's pretty much where the resemblance ends. For one thing, they had claws, not hooves; their bodies were also stockier, albeit with long limbs that may have given them a certain agility.
Sunday, 9 March 2025
Gorilla Communities
There are many factors that we need to consider when attempting to reverse this, and some of them also have a bearing on the evolution of our own species. Among these is the question of how gorilla groups are socially constructed and how they interact. It turns out that here, we can't just consider "gorillas" en masse because the two species behave in very different ways. For example, while one species can have multiple silverback males in the same troop, this is rare (but not unheard of) in the other.
Sunday, 2 March 2025
Delphinids: Spotted, Striped, and Spinning Dolphins
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Pantropical spotted dolphin |
It was first created in 1866 as a subgenus within Steno, the "narrow-beaked" dolphins, and contained just one species. It became a full genus in 1934,and by the end of the 20th century was agreed to contain five species - all of which had, in fact, been named before 1866. Since then, our understanding of genetics has greatly improved, and it has become clear that these various species cannot be so neatly arranged on a family tree as we might like.
Sunday, 23 February 2025
Wolves, Foxes, and Food
But the basic idea holds, and apex predators - those that are large enough that nothing else normally eats them - exist in much smaller numbers than herbivores or smaller carnivores. This means that, relative to their numbers, they have a disproportionate effect on the ecosystem within which they live. Take away the apex predators and, even though there weren't very many of them to begin with, you will radically change the local ecology.
And, because they are relatively few in number, apex predators tend to be especially vulnerable to being wiped out. That's even assuming that humans don't focus on them deliberately out of fear, whether for their own lives or for the good of their livestock. Globally, apex predators are declining. (On this blog, we're mostly interested in mammals, but consider, for example, that at least eight of the 23 species of crocodile/alligator are currently thought to be endangered).