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

PeerJ. 2023 Aug 30:11:e15915. doi: 10.7717/peerj.15915. eCollection 2023.

Abstract

Intraspecific variation modulates patterns of resource use by species, potentially affecting the structure and stability of food webs. In human-modified landscapes, habitat disturbance modifies trophic interactions and intraspecific niche variation, impacting population persistence. Here, we investigated the relationship of sex, ontogeny, and habitat factors with the trophic niche of Caiman crocodilus in an agricultural landscape. We evaluated temporal variation in the trophic niche parameters using carbon and nitrogen stable isotope analysis from different body tissues. We found that caimans exploit the same carbon and nitrogen pools through time, with low isotopic variability between seasons, partly due to the slow isotope turnover rates of tissues in crocodilians. Conversely, the trophic niche of caimans varied across habitats, but with no evidence of a difference between natural and anthropogenic habitats. It apparently results from the influence of habitat suitability, connectivity, and caiman movements during the foraging. Our findings highlight the broader niches of juvenile caimans relative to adults, possibly in response of territorialism and opportunistic foraging strategy. Although using similar resources, females had a larger niche than males, probably associated with foraging strategies during nesting. Considering the sex and body size categories, caimans occupied distinct isotopic regions in some habitats, indicating apparent niche segregation. Ontogenetic trophic shifts in the isotopes (δ13C and δ15N) depended on sex, leading to resource partitioning that can potentially reduce intraspecific competition. Decision-makers and stakeholders should consider the trophic dynamics of sex and body size groups for the sustainable management and conservation of caiman populations, which implies in the maintenance of wetland habitats and landscape heterogeneity in the Formoso River floodplain.

Keywords: Anthropogenic habitats; Caiman crocodilus; Niche temporal variability; Ontogenetic shifts; Sexual niche variation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Agriculture*
  • Alligators and Crocodiles*
  • Animals
  • Body Size
  • Carbon
  • Female
  • Humans
  • Male
  • Nitrogen
  • Nitrogen Isotopes

Substances

  • Carbon
  • Nitrogen
  • Nitrogen Isotopes

Grants and funding

This study received funding from Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—CAPES, Finance Code: 001, PhD; Programa de Doutorado Sanduíche no Exterior (PDSE)—CAPES [Process Number 88881.357613/2019-01]; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Edital CAPES 25/2014—Pró-Forenses [Project Number 23038.006832/2014-11]; Conselho Nacional de Desenvolvimento Científico e Tecnológico—CNPq [Award Number: 140284/2018-4]; The Rufford Foundation [Award Number 23971-1]; Programa de Pós-Graduação em Ecologia da Universidade de Brasília; Fundação de Apoio à Pesquisa do Distrito Federal (FAPDF), and the USAID’s PEER program under cooperative agreement [grant number AID-OAA-A-11-00012]. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.