Abstract
An ecosystem engineer is an organism that creates or modifies habitats
for other species. Numerous research has reported that the abundance of
species in the physical structures created by ecosystem
engineers—referred to as engineered habitats—is higher than in other
typical habitats—referred to as non-engineered habitats—suggesting
the importance of the roles ecosystem engineers play in the population
demography of species utilizing engineered habitats (i.e., utilizing
species). However, it remains largely unknown whether engineered
habitats, in comparison to non-engineered habitats, are more suitable
for the survival and growth of the utilizing species. In this study, we
addressed this issue by assessing the suitability of wallow, created by
Japanese sika deer (Cervus nippon yesoensis), as an alternative larval
habitat for Rana pirica frogs and Hynobius retardatus salamanders that
oviposit their eggs in the deer wallows. We compared the early life
history performance (i.e., from egg to mid-larval stage) of the two
amphibian species in the deer wallows and in non-engineered natural
ponds. Our survey revealed that R. pirica frogs survived better in
wallows than in ponds, while H. retardatus salamanders survived better
in ponds than in wallows. Additionally, R. pirica frogs had a smaller
size at metamorphosis and a longer time until metamorphosis in wallows
than in ponds. The species-specificity (i.e., survival of frogs vs.
survival of salamanders) and the trait-specificity (i.e., survival vs.
growth of frogs) in the suitability of deer wallows represent the
complexity of the effects of ecosystem engineers on the utilizing
species. For example, the contrasting suitability of deer wallows for
the survival of the two amphibian species suggests that sika deer may
have distinctive effects on the population demography of the two species
by creating wallows that function as refuges and ecological traps for R.
pirica frogs and H. retardatus salamanders, respectively.