Safe caves and dangerous forests? Predation risk may contribute to salamander colonization of subterranean habitats

Abstract

Recent studies suggest that many organisms actively colonize the subterranean environment to avoid climatic stress, exploit new ecological opportunities and reduce competition and predation. Terrestrial salamanders are known to colonize the more stable subterranean habitats mainly to escape external climatic extremes, while the role of predation avoidance remains untested. To better understand the importance of predation, we used clay models of the cave salamander Speleomantes strinatii to compare the predation occurring in woodland and subterranean habitats. Models were positioned in three forests and in three caves in NW Italy. One-hundred eighty-four models were retrieved from the field and 59 (32%) were attacked by predators. Models were attacked on their head more often than expected by chance and, therefore, were perceived by predators as real prey items. In the woodlands, clay models showed a four-time higher probability of being attacked in comparison to caves, suggesting a different level of potential predation risk in these surface habitats. These findings are one of the first experimental evidences that, in terrestrial ecosystems, predation avoidance may contribute to the salamander underground colonization process.

Do Salamanders Limit the Abundance of Groundwater Invertebrates in Subterranean Habitats?

“…Thus sectors close to the surface and surface habitats themselves can provide useful trophic resources for stygobionts which, in favorable seasons or with particular environmental conditions, can occupy springs or move closer to the cave entrance. At the same time, areas at the boundary between underground and surface environments can be more risky in terms of climatic variation (they are unstable compared to deep subterranean habitats) and predator occurrence [57,58]. Our results suggest that when a top-predator occurs in subterranean habitats, it may severely limit the abundance of stygobiont fauna, since all the three target taxa considered in this study showed a significant lower abundance in sites with fire salamander larvae.…”

Variability of A Subterranean Prey-Predator Community in Space and Time

“…Our study habitat had a recent origin, being only 70 years old, and its physical structure was relatively simple, possessing only one large entrance and being horizontal. Furthermore, the entire ecological community was constituted by non-specialized (or "troglophile" sensu [37]) forest or soil animals that colonize opportunistically newly created subterranean habitats in search of new ecological opportunities, to avoid unfavorable climatic conditions, or to reduce competition and predation [38][39][40]. Our study showed a general constancy in both composition and distribution along the cave of the entire faunal community, at least during the seven-year period investigated.…”

The population ecology and behavior of the cave salamander, Eurycea lucifuga (Rafinesque, 1822).

“…obs.). However, Salvidio et al (2017) similarly reported caves to be safer habitats than surrounding forests for the troglophilic salamander H. strinatii. Specifically, predation risk, as determined by damage to clay models, was about four times greater in forested areas compared to caves (Salvidio et al, 2017); in my study, damage to clay models was 2.6 times greater in forests than in caves.…”

“…However, Salvidio et al (2017) similarly reported caves to be safer habitats than surrounding forests for the troglophilic salamander H. strinatii. Specifically, predation risk, as determined by damage to clay models, was about four times greater in forested areas compared to caves (Salvidio et al, 2017); in my study, damage to clay models was 2.6 times greater in forests than in caves. Further, just over half of the damage (53.6 %) to models in forests was from rodents, some of which are nocturnal and are likely to interact with Cave Salamanders both inside and outside caves; in fact, damage from rodents was the most prevalent damage type, occurring in both caves and forests.…”

“…This is implicated in the colonization of subterranean environment by the Mexican Tetra, Astyanax fasciatus mexicanus (de Filippi, 1853), avoiding fish-eating bats (Romero, 1985), and in the choice of breeding habitat by the Fire Salamander, Salamandra salamandra (Linnaeus, 1758), in predatorfree cave streams (Manenti et al, 2016). Salvidio et al (2017) addressed the concept that cave inhabitance by the European Cave Salamander, Hydromantes [Speleomantes] strinatii (Aellen, 1958), is partly due to the safety caves provide. Specifically, they suggested higher levels of predation risk in forests resulted in the colonization of caves by this troglophilic species.…”