Notes on the Short-tailed Bat (Mystacops tuberculatus)
[Read before the Canterbury Philosophical Institute, 1933; received by the Editor, December 15, 1935; issued separately, September, 1936.]
In Hutton and Drummond's Animals of New Zealand the authors refer to the short-tailed bat as “on the brink of extinction, and (it) may indeed even now have ceased to exist,” adding: “Many years have passed since one of the species was recorded. Away in February, 1871, when H.M.S. ‘Clio' was in Milford Sound several of these bats were caught when the sail were being loosed to dry.” They give three other records of specimens, and that about completed the knowledge of the species when the book was published in 1904. The authors speculate on the habits of the bat, and suggest that the peculiar structure of its wings indicates that it may seek its prey by creeping about on tree-trunks and branches as well as on the wing. It is interesting to be able to record after the lapse of twenty-eight years that the short-tailed bat is still in existence, and that, from the little I know of its habits, it seems that Hutton and Drummond's surmise that it might at times walk after its prey is probably correct.
In 1929 when I informed Mr H. Guthrie-Smith that I was going down to stay on Cundy Island, one of the small islands off the west coast of Stewart Island, he told me that when he had been in that locality some years previously he had seen a bat of larger size than the common long-tailed mainland species.* On Cundy Island, where I stayed for a month, we saw no bats of any kind, but I was told by several people from Bluff that bats were still plentiful in some of the islands further south.
In 1931, together with two friends, I spent five weeks of November and December on Solomon Island in the huts at Bat Bay. This little bay receives its name from the fact that a cave in the low granite cliffs that surround it was the home of thousands of bats twenty years ago. The story goes that some mutton-birders set fire to an old mattress in this cave, smoking all the bats out of it, and that they have never returned. We investigated its interior, and many more around the shore of this and other islands nearby, but found no bats in any of them. Personally, I incline to the view that it was some cause other than the burning of the mattress that reduced the numbers of bats, possibly an introduced epidemic.
One day when looking for parrakeets' nests I shone an electric torch into a hole in a limb of a rata (Metrosideros lucida), and saw a cluster of bats huddled together at the end of it. The branch was about eleven inches in diameter and grew almost horizontally about five feet above the ground. The orifice was on the side of
[Footnote] * It is, unfortunately, no longer correct, perhaps, to refer to the long-tailed bat (Chalinolobus morio) as a common species, for it is quite gone from most districts, and is rapidly becoming scarcer in those where it still remains.
the branch facing south, and was about six inches long by two and a-half wide, with its greater length horizontal. The cavity within was roughly five inches in diameter and about eighteen inches long. We could count five bats huddled together filling the end of the cavity, and we left them, intending to come back on a moonlight evening to observe them. Two days later when passing the tree we found that the bats had gone, and though we looked into the hole whenever we passed for the next fortnight, they had not returned. The colour of their fur, which was the same as that of a mouse and lighter than that of the long-tailed bat, and their large rounded ears led us to believe that they were short-tailed bats.
I had taken with me to the island some aceytlene lamps with large motor-car headlight reflectors to use in the identification of petrels in the air at night, and when using these on one occasion from 10 p.m. to midnight on an open point of land we saw several bats flit by close to the ground. At odd times, too, one would fly past us when we were out at night in the bush, but always close to the ground. We did not see a great many, but none that we did see was flying higher than ten feet above the ground. We never saw one at dusk nor before it was quite dark, say, 10 p.m. (summertime). The flight is not so rapid as that of the long-tailed bat, nor is it so twisty; but the artificial light by which all our observations were made may have accounted partly for this difference. Another most interesting point is that this bat does not (on Solomon Island, at any rate) fly about at dusk, but only after dark, and continues to do so until midnight. This habit may be due to the fact that at dusk—the normal flight-time of bats in general—the air is too full of flying mutton-birds for the bat's comfort. One evening we were sitting in the hut when a bat flew in at the open door, fell into the edge of the low fire burning on the hearth, and fluttered to the side of the fireplace. I jumped up to catch it, but it flew out of the door again before I could reach it.
In another hollow rata some distance from the bats' tree there was a morepork's nest with young, and I used to examine the contents of this nest whenever I passed to get an idea of the diet of the birds. One day I found, besides the remains of two diving petrels, a fine specimen of a short-tailed bat, dead, but with only a small claw-puncture in its neck.
Ten days later we were passing bat tree, and, looking in, saw the cluster of bats at the end of it. We cut an entrance into the cavity and took out the bats, of which there were seven, males and females. They bit our fingers with their needle-like teeth and gave vent to shrill squeakings, opening their large rounded mouths and threatening us. It was in the late afternoon when we found them, and they were very sluggish in their movements, with the webs of their wings cold to the touch; indeed, their whole demeanour suggested that they were stiff and semi-comatose as a result of cold, although it was not an unusually cold day for the locality. They livened up considerably on the way back to the hut, and when we got there they were lissome and active and quite warm to the touch. We put them in a box with a wire-netting front, and they became most active in their efforts to escape. They run, head first, with a
curious stiff action and quite fast, using their folded wings as forelegs, the wrist-joint coming in contact with the ground. They climbed the wire-netting or the smooth wooden sides of the box tail-first with remarkable facility. As they kept trying to make a cluster of themselves in the corner of the box, I put in a top corner of the cage a tubular corrugated cardboard bottle-cover, and into this they soon found their way. A tin of water and the body of a diving petrel I had skinned were also put into the cage, and next morning some of the flesh had been eaten. This was the only time they ate anything in the five days we had them, remaining in their cardboard house all day, and apparently usually all night, for I only once or twice heard any movement in the box when I went past it in the dark or shone my torch in. We tried them with dead flies, but these were not taken; nor white grubs which we got out of our firewood when chopping it. When handled after an interval of two days the bats were again found to be cold and stiff as when we first took them out of their tree.
It is said that these bats climb about the trees in search of their food, and I can well believe it from the activity with which they ran and climbed about in their box. One day in a hollow in the side of a rata I found a bell-bird's nest containing three dead young. They had just begun to get their feathers, but the flesh had been neatly eaten off their backs, leaving the vertebrae and the upper part of their ribs exposed. This may have been done by bats, though it may also have been the work of beetles or even the big brown slugs.
These bats were not uncommon on Solomon Island, and are probably on Pukeweka and Big South Cape as well. Mr J. Morrison tells me that a cave on Kaimohu was full of bats years ago, and they would probably be this species. I think it reasonable to assume that black rats would be inimical to the welfare of these bats, and if that is so, then the islands available as homes for bats are very limited, for there are only six or seven islands of any size in that locality not inhabited by rats. From the stories one hears of the great flocks of bats in some caves many years ago it would seem that there has been a considerable reduction in their numbers; yet if they do seek their food by climbing about in trees after it, then we would have had a very poor chance of seeing them, and they may be much more plentiful than we imagine.
In December, 1932, I spent a fortnight on Jacques Lee's Island, to the east of Stewart Island, where there are neither rats nor cats. One day when I was examining a hollow in a rata for birds' nests I noticed the unmistakable musty odour of these bats. The entrance to the hollow was on the side of the branch, and the cavity extended about three feet down to the trunk of the tree, which was also hollow. Some days later we cut a hole into this trunk to examine it. We did not find any bats, but in the base of the tree there was a great accumulation of their droppings. On this island, too, we saw bats when out with our searchlights at night, but here again we never saw one before 10 p.m., and those we did see were flitting about among the tree-stems and not flying about the tree-tops. We did not actually handle one of them, but I have no doubt from their
behaviour that they were the short-tailed species. If that is so, it is very probable that they are also on other islands in the vicinity which are free from rats and cats.
On Codfish Island, to the west of Stewart Island, I found a large totara tree in which a great cavity had been much tenanted by bats, for there were several bushels of bat-droppings in it. There were no bats in the hollow when I found it, but they had certainly been there within a few weeks. It seems likely that the bat on Codfish Island is the short-tailed species, for none of my party saw any bats on this island, and we probably should have done had they been long-tailed, as these would almost certainly have hunted insects in the clearing near our camp.
In discussing the matter with mutton-birders, who annually visit the islands, I have been able to gather a few scraps of information concerning the numerical status of these bats. It seems that prior to about 1910 they were very numerous on at least two of the islands on the south-west of Stewart Island; at about that time there was a sudden diminution in their numbers, and since then they have been rarely met. I think it likely that the superiority of our lights would enable us to see more of them at night than the mutton-birders would see with their small lamps. The fact that these bats have survived in fair numbers for over twenty years from the time when they first became comparatively scarce leads one to hope that they will continue to do so.