The cost of chemical defence

the impact of toxin depletion on growth and behaviour of cane toads (Rhinella marina)

Ryann A. Blennerhassett, Kim Bell-Anderson, Richard Shine, Gregory P. Brown*

*Corresponding author for this work

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Many animals capable of deploying chemical defences are reluctant to use them, suggesting that synthesis of toxins imposes a substantial cost. Typically, such costs have been quantified by measuring the elevation in metabolic rate induced by toxin depletion (i.e. during replenishment of toxin stores). More generally, we might expect that toxin depletion will induce shifts in a broad suite of fitness-relevant traits. In cane toads (Rhinella marina), toxic compounds that protect against predators and pathogens are stored in large parotoid (shoulder) glands. We used correlational and experimental approaches in field and laboratory settings to investigate impacts of toxin depletion on growth rate and behaviour in cane toads. In free-ranging toads, larger toxin stores were associated with smaller gonads and livers, suggesting energetic trade-offs between toxin production and both reproduction and energy metabolism. Experimental removal of toxin (by manually squeezing parotoid glands) reduced rates of growth in body mass in both captive and free-ranging toads. Radio tracking demonstrated that de-toxined toads dispersed more slowly than did control toads. Given that toxin stores in cane toads take several months to fully replenish, deploying toxin to repel a predator may impose a substantial cost, explaining why toads use toxin only as a final line of defence.

Original languageEnglish
Article number20190867
Pages (from-to)1-9
Number of pages9
JournalProceedings of the Royal Society B: Biological Sciences
Volume286
Issue number1902
DOIs
Publication statusPublished - 1 May 2019
Externally publishedYes

Keywords

  • Bufo marinus
  • parotoid glands
  • radio telemetry
  • toxin production
  • toxin replenishment

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