Predaceous Diving Beetles (Coleoptera: Dytiscidae) May Affect the Success of Amphibian Conservation Efforts

The role of invertebrate predation in shaping vertebrate communities is often underestimated or overlooked, which has resulted in the lack of their recognition in conservation planning. This is evident with predaceous diving beetles (Coleoptera: Dytiscidae) which are often the top predator in many aquatic freshwater habitats. During weekly monitoring of a compensatory habitat reintroduction for an endangered frog species, a group of a dozen adult diving beetles were encountered attacking and quickly dismembering and consuming a tadpole. A single adult diving beetle was also discovered burrowing its head deep inside and consuming a tadpole approximately three to four times its size. Although Dytiscidae are known to occasionally consume vertebrates such as tadpoles, adults are typically considered scavengers, and this communal predatory behavior and feeding method have not been previously documented. Besides these interesting novel behaviors, these observations may have implications for amphibian conservation since management efforts are not typically concerned with naturally occurring ubiquitous threats such as those from small invertebrate predators, as it is rarely been observed in nature. However, this may be perhaps due to their ability to consume prey rapidly, especially if predating in groups. Although amphibian conservation plans expect some losses from natural predation, diving beetles may affect conservation efforts such as captive breeding and reintroductions with populations already on the threshold of extinction and where every individual critical to success.

Predaceous Diving Beetles (Coleoptera: Dytiscidae) May Affect the Success of Amphibian Conservation Efforts

During weekly monitoring of a compensatory habitat reintroduction for an endangered frog species, a group of a dozen adult diving beetles (Coleoptera: Dytiscidae) were encountered attacking and quickly dismembering and consuming a tadpole. A single adult diving beetle was also discovered burrowing its head deep inside and consuming a tadpole approximately three to four times its size. Although Dytiscidae are known to occasionally consume vertebrates such as tadpoles, adults are typically considered scavengers, and this communal predatory behavior and feeding method have not been previously documented. Besides these interesting novel behaviors, these observations may have implications for amphibian conservation since management efforts are not typically concerned with naturally occurring ubiquitous threats such as those from small invertebrate predators, as it is rarely been observed in nature. However, this may be perhaps due their ability to consume prey rapidly, especially if working in packs. Although amphibian conservation plans always expect some losses from natural predation, diving beetles may seriously affect conservation efforts such as captive breeding and reintroductions with populations already on the threshold of extinction and where every individual critical to success.

Predaceous Diving Beetles (Coleoptera: Dytiscidae) May Affect the Success of Amphibian Conservation Efforts

During weekly monitoring of a compensatory habitat reintroduction for an endangered frog species, a group of a dozen adult diving beetles (Coleoptera: Dytiscidae) were encountered attacking and quickly dismembering and consuming a tadpole. A single adult diving beetle was also discovered burrowing its head deep inside and consuming a tadpole approximately three to four times its size. Although Dytiscidae are known to occasionally consume vertebrates such as tadpoles, adults are typically considered scavengers, and this communal predatory behavior and feeding method have not been previously documented. Besides these interesting novel behaviors, these observations may have implications for amphibian conservation since management efforts are not typically concerned with naturally occurring ubiquitous threats such as those from small invertebrate predators, as it is rarely been observed in nature. However, this may be perhaps due their ability to consume prey rapidly, especially if working in packs. Although amphibian conservation plans always expect some losses from natural predation, diving beetles may seriously affect conservation efforts such as captive breeding and reintroductions with populations already on the threshold of extinction and where every individual critical to success.

Informing compensatory habitat creation with experimental trials: a 3-year study of a threatened amphibian

The creation or restoration of habitat to mitigate biodiversity loss is a common conservation strategy. Evidence-based research via an extensively monitored trial study should be undertaken prior to large-scale implementation to predict success and identify potential limiting factors. We constructed an experimental trial habitat for the threatened green and golden bell frog Litoria aurea, in Australia, to inform a broader programme of compensatory habitat creation. Individuals were released into the trial plot and a nearby natural wetland for comparison to determine if the created habitat would support their growth, survival and persistence. Half of the trial waterbodies were enclosed within an exclusion fence to separate the effects of habitat suitability from ecological processes. We found the habitat provided L. aurea with sufficient resources to grow, survive and persist for 3 years. However, no breeding occurred, and further investigations need to focus on understanding the drivers of reproduction. Although a disease outbreak occurred during the study, persistence continued for the next 2 years. This was attributed to the large number of individuals released, a strategy we recommend for future mitigation strategies to account for low survival and high turnover rates. Dispersal probably affected abundance in the unfenced areas, and landscape-level initiatives are suggested for this species. This study demonstrates that experimental trials are valuable, as they can inform future habitat management by identifying limitations that could hinder success prior to the implementation of large-scale initiatives.

Challenges in Using Habitat Equivalency Analysis for Scaling Compensatory Restoration

ABSTRACT Some oil spills cause losses of ecological services in coastal wetlands, other shoreline environments, intertidal ecosystems, and upland environments. In the United States, habitat equivalency analysis (HEA) is being used frequently in natural resource damage assessments for such oil spills to determine the scale of compensatory-restoration projects needed to offset the ecological service losses. The cost of the scaled compensatory-restoration project(s) that offset the ecological service losses is the measure of natural resource damages for the lost ecological services. Our paper describes the HEA process and provides an example of its application. Then we examine several challenges that arise in some HEA applications, including the role of leasing versus purchasing compensatory habitat, increasing values of compensatory habitat over time due to decreasing availability, accounting for service gains from compensatory habitat in the distant future when the present value of those services is essentially zero, and addressing uncertainties in estimating HEA inputs (such as the magnitude of annual service losses and gains). The final section of our paper provides our conclusions with respect to these challenges.