Young copperheads are known to feed upon ant-eating frogs occasionally
(Anderson, 1942: 216; Freiburg, 1951: 378). Other kinds of snakes
supposedly eat them also. The common water snake (_Natrix sipedon_) and
garter snake (_Thamnophis sirtalis_) probably take heavy toll of the
adults at the time they are concentrated at the breeding pools. Larger
salientians may be among the more important enemies of the breeding
adults, the tadpoles, and the newly metamorphosed young. Bullfrogs
(_Rana catesbeiana_) and leopard frogs (_Rana pipiens_) are normally
abundant at the pond on the Reservation. These large voracious frogs
lining the banks are quick to lunge at any moving object, and must take
heavy toll of the much smaller ant-eating frogs that have to pass
through their ranks to reach the water. The newly metamorphosed young
often are forced to remain at a pond's edge for many days, or even for
weeks, by drought and they must be subject to especially heavy predation
by ranid frogs. Even the smallest newly metamorphosed bullfrogs and
leopard frogs would be large enough to catch and eat them.
As a result of persistent drought conditions in 1952 and 1953, bullfrogs
were completely eliminated from the pond by early 1954. Re-invasion by a
few individuals occurred in the course of the summer; these probably
made long overland trips from ponds or streams that had persisted
through the drought. Leopard frogs reached the pond in somewhat larger
numbers, but their population in 1954 was only a small percentage of
that present in most other years. Notable success in the ant-eating
frog's reproduction in 1954 may have been due largely to the scarcity of
these large ranids at the breeding ponds.
Freiburg (_loc. cit._) noted that many of the ant-eating frogs he
examined were scarred, and some had digits or limbs amputated. He did
not speculate concerning the origin of these injuries. However, it seems
likely that many or all of them were inflicted by the short-tailed shrew
(_Blarina brevicauda_). Five-lined skinks living on the same area were
likewise found to be scarred by bites which I identified (Fitch, 1954:
133) as bites of the short-tailed shrew. This shrew is common on the
Reservation, especially in woodland. Many have been trapped in the
pitfalls. On several occasions when a short-tailed shrew was caught in
the same pitfall with ant-eating frogs, it was found to have killed and
eaten them. Like the frogs, the shrews were most often caught in
pitfalls just after heavy rains. Once in 1954 a shrew was found at the
quarry in a pitfall that had been one of those most productive of frogs.
The bottom of the pitfall was strewn with the discarded remains (mostly
feet and skins) of perhaps a dozen ant-eating frogs. All had been eaten
during one night and the following morning, as the trap had been checked
on the preceding day. On other occasions shrews caught in pitfalls with
several frogs had killed and eaten some and left others unharmed.