What a great group of readers I have! I complained about my dearth of fox pictures, and what happens? Ceiling Cat sends me readers bearing gifts of fox pictures and videos, including species other than Vulpes vulpes. In fact, I now have more than enough pictures for a week; but if you have some good ones, I’ll still accept them.
Today I’m featuring species besides the familiar red fox (but Reynard will return). First, we have three bat-eared foxes (Otocyon megalotis) from reader Bob Johnson, photographed by him in Kenya in 2008 (click to enlarge):
The bat-eared fox has a disjunct range in Africa, with each of its two regions representing a separate subspecies (O. m. megalotus in the south and O. m. virgatus in the east). Its ears are large (about 13 cm, or 5 inches), as is usual for foxes inhabiting warmer climes.
The observation of longer extremities in related species (or in populations of a single species) in warmer habitats is called “Allen’s rule.” It holds for warm-blooded animals like mammals and birds, and that should be a clue to its evolutionary significance. Try to guess the answer without Googling. There two possible answers, both of which may hold:
Like the fennec below, the bat-eared fox is largely insectivorous, dining mainly on termites. It’s also monogamous and, unusually, males do most of the parental care—at least according to Wikipedia.
The fox with the longest ears relative to body size is the fennec (Vulpes zerda), which lives in the Sahara desert (the reason for those crazy ears). The species is nocturnal, and 80% of its diet consists of termites.
It’s the smallest of all foxes (1.5-3.5 lb, or 0.7-1.6 kg), weighing less than an average housecat. It’s my favorite of all foxes because it’s adorable, furry, and the most catlike of canids. Here are two pictures taken from the web. The second is a cub, whose ears look even more ridiculous because all dogs and cats have relatively larger ears when they’re young:
The species name is Vulpes lagopus, and it has a pan-Arctic range:
As you see, this species has much smaller ears, and the selection pressures involve at least one environmental factor that drove the evolution of large ears in desert foxes. Its tail is also bushy, and during the cold Arctic winters (animals can tolerate temperatures of -50 C), it wraps its tail around its head like a muffler. It’s snout is also relatively less pointed than that of foxes in more temperate climes—for the same reason why the ears are small.
Unlike the fennec or bat-eared fox, this one is a carnivore, dining on small mammals like rabbits, mice, and voles.
Another adaptation of this species is that, like many Arctic birds and mammals, it changes color with the seasons, being white (as above) during winter, and turning grey or brown in summer. That is also adaptive and simply can’t be explained by genetic drift (pay attention, Larry Moran!), for it’s a parallel trait seen in many Arctic animals. And the adaptive significance is clear.
There are also two morphs: the regular one (‘white’) and a ‘blue’ morph that lives in more coastal regions, though both can be found in the same place, as seen in the picture below. The blue color is due to homozygosity for a single recessive gene. Blue foxes, prized for their pelts, were moved to the Aleutian Islands en masse to try to preserve the morph.