NATURAL HISTORY By Kate Warren and Ian MacQuarrie nimals have a variety of gaits, with woods. They are very similar in size and very sensibly, in hibernation. A the pattern employed depending colour: brown backs, yellow sides shad- Aside from the tail tips, what are the upon habitat and circumstance. More- ing to white underneath. The easiest way main differences between the two spe- over, since much knowledge of the life to tell them from the runners is by their cies? Evolution theory suggests that and times of a species comes from inter- tails, which are longer than their bodies. there must be some dissimilarities, or preting tracks, some attention to the It is safe to assume that any mouse with else one would compete strongly against, dancing feet that make them is useful such a long tail is a jumping mouse. and perhaps eliminate, the other. There and often necessary. Basic biology, then, And how do you tell the jumping mice are, of course, differences in preferred is not just counting teeth; it is looking at apart? Again, the tail distinguishes them: habitat between woodland and meadow toes, and how these are picked up and the woodland jumping mouse has a white- jumpers, but they also differ in social put down. tipped tail, the meadow jumping mouse customs, behaviour. Both species are For instance, there are six species of does not. Such minor differences may b e somewhat nomadic, but the grassland small rodents on Prince Edward Island lost on your cat, but they are mighty jumper is usually found alone, while the that can generally be called "mice." handy for naturalists. woodland type is much more sociable, These may be classified in many ways, These colour schemes are thus any- even colonial, with its fellows. It is also such as by colour, size, similarity to thing but mousy; they add to the charm more of a burrower, excavating tunnels Mickey. Their teeth provide useful infor- of an encounter with a jumper. Perhaps a few centimetres below the surface. mation, particularly in terms of proper you have seen one while walking along Thus, there are sufficient differences and improper mouse-handling tech- the edge of a hayfield or in the rough between the Island's jumping mice to nique. They can also be divided into ground around a marsh. A tiny projectile ensure that species-threatening compe- cursorial (running) and saltatory rockets from under your feet and bounds tition does not occur. (jumping) groups. As most housekeep- off in a zigzag pattern. A jumping mouse ers can attest, the field mouse and house in good condition can leap more than mouse are cursorial types. The jumpers three metres, or perhaps 15 times its The Mouse that Soared are less familiar. body length. It quickly goes to ground, relying on its camouflage for protection. Jumping is a useful evasive action, and If you leave it alone, it will go back to its many animals that normally walk or run Small Differences summer schedule of eating (mostly seeds will jump for sheer survival when threat- or fruit), sleeping (in a nest of grass ened. Adaptations for jumping may be Prince Edward Island enjoys two species under some cover), and reproducing more or less developed, varying from of jumping mouse. One of these is a (one to three litters averaging five young the strengthened hind limbs of rabbits grassland lover; the other prefers the each). Both species spend the winter, and hares to a shifting of the centre of 17 gravity toward the posterior, as in kanga- in general the more elastic they are, the Ontario eastwards. Neither species is roos. In jumping mice, such physical more energy can be stored in them. listed as native to Newfoundland, al- adaptations include a shortened body, a The Achilles tendon of jumpers tends though both could probably live there if greatly lengthened tail, and partial fus- to be larger and more elastic than that of introduced. ing of the bones of the foot to provide a non-jumpers. When an animal lands af- better kick-off. ter the first jump, the tendon is stretched There are internal adaptations as well, and energy is stored for use in the next . and Counting relating to the elasticity of tendons and take-off. This energy-return system al- ligaments. The distance that an animal lows for more and longer jumps, as the No one knows much about how many can jump may depend less upon size or designers of sneakers seem to have jumping mice there are on Prince Edward strength than upon this elasticity. To suddenly realized. Jumping thus pro- Island. In 1978, Bateman and Prescott understand this, think of a n elastic band: vides good manoeuverability with a found that the woodland jumping mouse when it is stretched, it acquires energy relatively low expenditure of energy — was rare in the Prince Edward Island (it is this energy you feel when the band provided the habitat is suitable. Do not National Park; in 1954, another author is released and hits your finger). The practise high jumps in low caves. had described it as "uncommon." On the more the band is stretched, the more Most of the rodents that jump are other hand, Wilson found this species to potential energy is stored in it. Of course, desert dwellers, such as gerbils and be quite common in woodlands in the rubber bands (and ligaments) kangaroo rats. Our local heroes are Montague area in 1988. Records from can be stretched exceptional in dwelling around wood- the University of Prince Edward Island's too .4&tfM^4iife* far> but lands and temperate grasslands. The Biology Department suggest that the meadow jumper ranges across Canada woodland jumper may be quite abun- from British Columbia to Nova Scotia; dant locally in some habitat types, but the woodland type is more of an that its numbers — even its presence — easterner, being found primarily from vary greatly from year to year. The Family Dipodidae on Prince Edward Island Meadow Jumping Mouse Woodland Jumping Mouse Scientific Name Zapus hudsonius acadicus | Napaeozapus insignis insignis Size Range Total length: 18-24 cm. | Total length: 23-30 cm. * Tail length: 13-16, cm... Weight: 12-25 g. Weight: 16-27 g Brown fur on back which fades to yellow : Similar to that of the meadow jumping Colouration on the sides and white on the belly. A - mouse, however, the tail is tipped with road band of darker fur may be present - white. on the back, running from nose to tail. Along streams or rivers in grasslands Generally found close to streams or J, Habitat or near marshes. rivers in both coniferous and hardwood i I forests. Reproduction \ 1-3 litters per year with an average of I 1-2 litters per year with an average of .^^JS^MM&P^ Utter. _ JAwwazMr Primarily seeds, but also fruit and Fruit (especially apples, berries), seeds, some insects. roots, insects, fungi. 18 A trick of the tail: the white-tail-tips identify these as woodland jumping mice. In the same studies, the meadow jumping mouse was described as abundant in the Na- tional Park, but was not found in the Montague woodlands. The contrasting population densi- ties are probably due to the differences in habitat: the woodland jumping mouse likes forest; the meadow jumper prefers the open spaces. But some mammalogists believe that population differences through time may be explained by the sort of life history strategy that these mice have developed. They are geared to adult over-winter survival, rather than to rapid reproduction and high popula- tion densities. In any case, there is no evidence that these winsome mice are endangered locally. Since they do not in any way menace human crops,* we can conclude that they are simply interest- ing, non-threatening, non-threatened species that share our Island way of life. Sources The general biology of the two jumpers is described in A. W. Banfield's classic The Mam- mals of Canada. Island information was ob- tained from Myrtle Bateman and Robert Prescott's Mammals of Prince Edward Island National Park, published by the Canadian Wildlife Service in 1984. In addition, the wood- land species turns up in Melvin Wilson's 1988 thesis (available in the Robertson Library) on the effects of forestry practices on small mam- mals in the Montague area. The topic of locomotion in animals is dis- Jumpingand Walking (1977) and R Alexander's Animal Mechanics (1968). Finally, we wish to thank all of the jumping mice that we have encountered on many local field trips, in live traps, or through the good graces of an obliging cat. im *Unlike their cousins, the meadow voles. See Ian MacQuarrie, "Plagues of Mice," Number 21 (Spring- Summer 1987). 19 .