Landscape features affect caiman body condition in the middle Araguaia River floodplain

Abstract

Landscape modifications often undermine habitat suitability for species’ persistence, with initial effects observed through the physiological responses of individuals and populations. However, some landscape features can allow tolerant wildlife species to persist in human‐modified landscapes, but they are still overlooked. Across distinct agricultural landscapes, we assessed landscape features affecting the body condition (estimate through scaled mass index ‐ SMI) of Caiman crocodilus (Crocodylia, Alligatoridae) in human‐modified landscapes of the Araguaia floodplain, central Brazil. We used a spatial Bayesian model averaging approach to determine the effects of landscape attributes, ectoparasites, tail damage and severe body injuries on caiman body condition. We found that caimans had higher SMI in anthropogenic (ditches and artificial ponds) than natural habitats (lakes or rivers). Overall, caiman SMI was negatively associated with wetland cohesion (an aggregation and connectivity metric). Otherwise, landscape composition did not influence caiman SMI. Further, ectoparasites and body injuries did not affect SMI, whereas tail damage negatively affected SMI. Our findings underscore that caiman populations can adapt to artificial wetlands and irrigated rice fields, provided they incorporate natural and semi‐natural habitat patches that enhance environmental heterogeneity, prey availability, and waterbody availability and connectivity.

Agricultural input modifies trophic niche and basal energy source of a top predator across human-modified landscapes

“…We acknowledge that this hypothesis has not been rigorously tested. Alternatively, a recent study shows that C 3 and C 4 plants have distinct AA ESS δ 13 C fingerprints (Besser et al, 2022), so the patterns shown in Figure 3 could be primarily driven by greater incorporation of C 4 resources caiman diets in anthropogenic habitats, ponds and ditches (Pereira et al, 2018;Pereira and Colli, 2022). Unfortunately, we cannot currently discriminate between these two explanations because AA ESS δ 13 C data are unavailable for local primary producers.…”

“…Here, we combined landscape attributes, species intraspecific traits, and isotope-based estimates of the trophic ecology of Caiman crocodilus (spectacled caiman) to investigate the anthropogenic impacts of landscape modification on the food webs of the Araguaia floodplain using a spatially explicit approach. Caiman crocodilus 10.3389/fevo.2023.1053535 (Crocodylia, Aligatoridae) is an indicator species and a model organism for detecting and monitoring environmental impacts in the Araguaia floodplain owing to its high detectability and seasonal and ontogenetic movements across a variety of terrestrial and aquatic habitats (Rosenblatt et al, 2013;Somaweera et al, 2020;Pereira and Colli, 2022). We assessed (1) the effects of intraspecific traits of sex, ontogeny, and habitat use based on the δ 13 C and δ 15 N isotopes values of C. crocodilus tissues; (2) the influence of landscape attributes (land-use composition and wetland configuration) on the isotopic niche of C. crocodilus; and (3) the influence of crop-derived (rice and soybean) energy on the food webs utilized by C. crocodilus in human-modified environments.…”

Sources of intraspecific variation in the isotopic niche of a semi-aquatic predator in a human-modified landscape

“…The occurrence of caimans in agricultural ditches and artificial ponds can suggest the incorporation of agricultural energy inputs, providing crop-derived carbon and affecting the energy flux and trophic relations in the whole food web ( Pereira, 2021 ). Pereira & Colli (2022) reported higher caiman body conditions in anthropogenic habitats, suggesting they favor foraging strategies and agricultural energy intake.…”

“…The trophic niche of crocodilians is influenced by several factors, including: ontogeny, as hatchlings feed primarily on aquatic and terrestrial invertebrate prey, juveniles increment smaller fishes and vertebrates in the diet, and adults consume more large vertebrates and fishes; flood pulse seasonality due to the high proportion of invertebrates in the wet season changing to a prevalence of fishes in the dry season ( Da Silveira & Magnusson, 1999 ; Magnusson, Da Silva & Lima, 1987 ; Thorbjarnarson, 1997 ; Thorbjarnarson, 1993 ); and sex due to sexual differences in habitat use and foraging area in the breeding period ( Barão-Nóbrega et al, 2016 ; Villamarín et al, 2011 ). Moreover, crocodilians take advantage of artificial or disturbed waterbodies, demonstrating ecological adaptability and resilience to persist in agricultural landscapes ( Borteiro et al, 2008 ; Marques et al, 2020b ; Pereira & Colli, 2022 ). Therefore, crocodilians are model organisms to detect and investigate the effects of human disturbance on the food web and assess the role of intraspecific trait variation on trophic dynamics.…”

“…Caiman crocodilus (Alligatoridae) inhabits a variety of natural wetlands ( e.g ., rivers, creeks, ponds, lakes, swamps, and marshes) and artificial waterbodies across their geographic distribution in Brazil, which comprehends the Amazon basin, Tocantins/Araguaia basins (central Brazil), and the Parnaíba and Coreaú basins in Ceará state (northeast Brazil) ( Farias et al, 2013 ; Velasco & Ayarzagüena, 2010 ). In the Araguaia basin, agriculture development impacts natural communities by replacing native vegetation with pastures and crops ( Garcia et al, 2017 ) and changing the hydro-geomorphological dynamics by water damming, pumping, and sedimentation ( Oliveira et al, 2015 ), implying in new ecosystems with modified habitats and landscapes to caimans occupy ( Pereira & Colli, 2022 ). Here, we investigate the relationship of sex, ontogeny, and habitat use factors with the trophic niche of C. crocodilus in a human-modified landscape of the Formoso River floodplain, a sub-basin of the middle Araguaia River basin.…”