Thermal constraints on foraging of tropical canopy ants
- 473 Downloads
Small cursorial ectotherms risk overheating when foraging in the tropical forest canopy, where the surfaces of unshaded tree branches commonly exceed 50 °C. We quantified the heating and subsequent cooling rates of 11 common canopy ant species from Panama and tested the hypothesis that ant workers stop foraging at temperatures consistent with the prevention of overheating. We created hot experimental “sunflecks” on existing foraging trails of four ant species from different clades and spanning a broad range of body size, heating rate, and critical thermal maxima (CTmax). Different ant species exhibited very different heating rates in the lab, and these differences did not follow trends predicted by body size alone. Experiments with ant models showed that heating rates are strongly affected by color in addition to body size. Foraging workers of all species showed strong responses to heating and consistently abandoned focal sites between 36 and 44 °C. Atta colombica and Azteca trigona workers resumed foraging shortly after heat was removed, but Cephalotes atratus and Dolichoderus bispinosus workers continued to avoid the heated patch even after >5 min of cooling. Large foraging ants (C. atratus) responded slowly to developing thermal extremes, whereas small ants (A. trigona) evacuated sunflecks relatively quickly, and at lower estimated body temperatures than when revisiting previously heated patches. The results of this study provide the first field-based insight into how foraging ants respond behaviorally to the heterogeneous thermal landscape of the tropical forest canopy.
KeywordsArboreal Behavior Formicidae Panama Sunfleck
We thank Oris Acevedo, Belkys Jimenez, and the staff of the Smithsonian Tropical Research Institute for logistical support in Panama. Amanda Winters assisted in the field. Comments from Jelena Bujan, Walter Carson, James Lichtenstein, and two anonymous reviewers improved the manuscript.
Author contribution statement
SPY, AYS, and BJA conceived and designed the experiments. MES, BJA, and AYS performed the experiments. SPY, MES, BJA, RK, and AYS analyzed the data. MK provided editorial advice, and all authors contributed to writing the manuscript.
This research was supported by National Science Foundation Grants DEB-1252614 to SPY, and DEB-0842038 and EF-1065844 to MK.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Human and animal rights
This article does not contain any studies with human participants or vertebrate animals performed by any of the authors.
- Denlinger DL, Yocum G (1998) Physiology of heat sensitivity. In: Hallman GJ, Denlinger DL (eds) Temperature sensitivity in insects and application in integrated pest management. Westview Press, Boulder, pp 7–54Google Scholar
- Diamond SE, Sorger DM, Hulcr J, Pelini SL, Toro ID, Hirsch C, Oberg E, Dunn RR (2012) Who likes it hot? A global analysis of the climatic, ecological, and evolutionary determinants of warming tolerance in ants. Glob. Change Biol 18:448–456. doi: 10.1111/j.1365-2486.2011.02542.x CrossRefGoogle Scholar
- Hemmings Z, Andrew NR (2016) Effects of microclimate and species identity on body temperature and thermal tolerance of ants (Hymenoptera: Formicidae). Austral Entomol.doi: 10.1111/aen.12215. (In press)
- Leigh EG Jr, Rand AS, Windsor DM (eds) (1996) The ecology of a tropical forest, 2nd edn. Smithsonian Institution, WashingtonGoogle Scholar
- Majerus ME, Majerus M (1998) Melanism: evolution in action. Oxford University Press, OxfordGoogle Scholar
- Meisel JE (2006) Thermal ecology of the Neotropical army ant Eciton burchellii. Ecol Appl 16:913–922. doi:10.1890/1051-0761(2006)016[0913:TEOTNA]2.0.CO;2Google Scholar
- Parker GG (1995) Structure and microclimate of forest canopies. In: Lowman MD, Nadkarni NM (eds) Forest canopies. Academic Press, San Diego, CA, pp 73–106Google Scholar
- SAS Institute Inc (2009) JMP statistical software version 11. SAS Institute, CaryGoogle Scholar
- Sinervo B, Mendez de la Cruz F, Miles DB, Heulin B, Bastiaans E, Villagrán-Santa Cruz M, Lara-Resendiz R, Martínez-Méndez N, Calderón-Espinosa ML, Meza-Lázaro RN (2010) Erosion of lizard diversity by climate change and altered thermal niches. Science 328:894–899. doi: 10.1126/science.1184695 CrossRefPubMedGoogle Scholar
- Vogel S (2013) Comparative biomechanics: life’s physical world. Princeton University Press, PrincetonGoogle Scholar
- Yanoviak SP, Silveri C, Stark AY, Van Stan JT, Levia DF (2016) Surface roughness affects the running speed of tropical canopy ants. Biotropica. doi: 10.1111/btp.12349. (In press)