Juvenile Newt Mortality & Population Viability

The following information came from this fascinating paper:
Neglected juveniles; a call for integrating all amphibian life stages in assessments of mitigation success (and how to do it), (Silviu O. Petrovan and Benedikt R. Schmidt, Biological Conservation 236 (2019) 252–260))

• Some juveniles apparently disperse diurnally in contrast to nocturnal dispersal in adults and their emigration has unpredictable timing and direction (they're not familiar with the landscape).
• Juveniles cross the road in the opposite direction of adults. In other words, when the rainy season starts, juveniles emigrate away from vernal pools to the highlands while the adults are migrating from the highlands toward the vernal pools and reservoir.
• Post-metamorphic juveniles are extremely small and are therefore more susceptible to dehydration on the road.
• Juvenile carcasses don't stay on the road long. One study found that 80% of the smaller bodied amphibian carcasses were gone from the road within 24 h. "... the combination of small, soft-bodied amphibians with warm, wet surfaces results in rapid carcass destruction, removal by scavengers or decomposition and thus leaves very little evidence of road mortality events (Santos et al., 2011; Zhang et al., 2018)."
• Some conservationists have found that amphibian population viability is not particularly sensitive to adult survival and mitigations directed towards post-metamorphic juveniles have stronger effects on population viability than those that improve adult survival.
• The authors state: "We conclude from the review of amphibian population models that there is substantial evidence that the fate of juveniles is critical and represents in many instances the driving factor for amphibian population dynamics... p 254
• The Gibbs & Shriver (2005) population model used by HTH takes into account juvenile survival rate. HTH used a hypothetical rate of 0.6 in their 2019 model. But it doesn't look like they're measuring the newts they're studying, so how will they differentiate juveniles from adults to come up with more than a hypothetical survival rate for juveniles?

Publicado el 18 de enero de 2021 por truthseqr