Unanticipated effect of climate change on an aquatic top predator of the Atlantic rainforest

Abstract

ABSTRACT1. From a biodiversity conservation viewpoint it is crucial to estimate the sensitivity of species and populations to climate change, especially of key species such as top predators.2. Here, the El Niño-Southern Oscillation phenomenon (ENSO) was used as a natural experiment to estimate the sensitivity of a population of the rainforest-dwelling broad-snouted caiman, Caiman latirostris, to extreme floods.3. Caiman abundance declined by 35% annually between 1996 and 1998, and then increased, without reaching 1996 levels, indicating a marked effect of the 1997 El Niño. Accordingly, the Southern Oscillation Index was positively correlated with caiman abundance, indicating lower caiman abundance with warm ENSO events.4. The relationship between the relative annual mean abundance of caimans and the maximum daily annual discharge of the Iguazú River was analysed. This relationship was parabolic, with caiman abundance increasing at discharges from 500 to 1500 m 3 s -1 and then decreasing at discharges from 1500 to 2500 m 3 s -1 , indicating an adverse effect of both extreme low and high river discharge. No effect of illegal hunting was measurable. 5. This study evaluated whether the negative effect of extremely high water levels on caiman abundance could be due to a decrease in the availability of the habitat more commonly used by small (<60 cm total length, TL) and medium (60-120 cm TL) caimans. Small and medium-sized caimans used herbaceous/shrub habitats more frequently than large caimans (>120 cm TL), i.e. the type of habitat flooded during extreme floods.6. An increase in extreme floods, as forecast for the Atlantic rainforest owing to climate change, may seriously affect the population of rainforest caimans through the reduction of adequate habitat for juveniles. This counterintuitive result, in which an excess of water reduces the abundance of an aquatic top predator, should be considered in conservation plans of rainforest-dwelling crocodilians.

Factors influencing detection, distribution and population dynamics of the broad-snouted caiman (Caiman latirostris) in an altered environment in north-eastern Brazil

“…Conversely, adverse weather conditions and rain may impact crocodylian behavior, for example, by limiting their opportunities for feeding or hindering emergence from shelters (Ahizi et al 2021; Strickland et al 2018). Heavy rainfall can also limit habitat availability for smaller individuals (Herrera et al 2015). However, recent studies on West African crocodile (Crocodylus suchus) suggest that precipitation can have positive effects on counts, possibly due to effects on prey availability, increasing crocodylians' foraging movements (Velo-Antón et al 2014); Nifong and Silliman 2017).…”

Broad‐scale climate variation drives the dynamics of animal populations: a global multi‐taxa analysis

“…One reptile species (green turtle Chelonia mydas in Australia) showed a significant association with ENSO + (Limpus & Nicholls, 1997) (Table 1), and two reptile species [a lizard ( Anolis apletophallus ) in Panama, broad‐snouted caiman ( Caiman latirostris ) in Argentina] had significant associations with ENSO − (Herrera, Solari & Lucifora, 2015; Stapley, Garcia & Andrews, 2015) (Table 1).…”

As particularidades da Região Trinacional a partir de sua gente: história, diversidade e identidade intercultural

“…O jacaré é considerado predador de topo de cadeia do sistema aquático na região trinacional. Ainda que seja pouco provável o seu desaparecimento local (não tão pouco provável, se somamos também outras pressões, como a caça), os predadores de topo de cadeia têm um papel determinante na constituição e no equilíbrio das comunidades animais abaixo deles, porquanto a drástica diminuição da população do jacaré poderia alterar as redes tróficas em conjunto (HERRERA et al, 2015) e isso implicaria a falta de balanços ecológicos com resultados imprevisíveis.…”