Abstract
My recent review examined the complex and intimate relationship between hermit crabs and the empty gastropod shells upon which they depend for survival. Because shells come with costs as well as benefits, the crabs are highly selective about which ones they prefer to occupy. Thus, a new shell is investigated and the information that is gathered appears to be compared with their existing shell before a decision is made. This is often prolonged and complex. Crabs also fight for shells and again the information that is gathered and used to inform fight decisions is complex. In my review, I consider these and other situations with reference to the possibility of sentience (including awareness). The excellent commentary from Mark Briffa expands on aspects of sentience and invokes the use of Lloyd Morgan’s Canon to avoid suggesting complex abilities when simpler explanations would suffice. I agree with this approach. However, I also suggest that when simpler explanations appear not to explain the data, then it is reasonable to consider if more complex mental abilities might be used. I also like Briffa’s suggestion that the use of an apparently higher mental faculty might result in a mechanism that is simpler than a large number of apparently simple decisions used to make complex decisions.
This is a preview of subscription content, log in via an institution to check access.
References
Arnott G, Elwood RW (2007) Fighting for shells: how private information about resource value changes hermit crab pre-fight displays and escalated fight behaviour. Proc Roy Soc B 274:3011–3017
Arnott G, Elwood RW (2009) Assessment of fighting ability in animal contests. Anim Behav 77:991–1004
Bateson M, Desire S, Gartside SE, Wright GA (2011) Agitated honeybees exhibit pessimistic cognitive biases. Current Biol 21(12):1070–1073
Briffa M (2022) When should we ascribe sentience to animals? A commentary on “Hermit crabs, shells and sentience” (Elwood 2022). Anim Cognit. https://doi.org/10.1007/s10071-022-01633-5
Briffa M, Elwood W (2000) The power of rapping influences eviction during hermit crab shell fights. Behav Ecol 11:288–293
Briffa M, Elwood RW (2001) Decision rules, energy metabolism and vigour in hermit crab fights. Proc Roy Soc B 268:1841–1847
Briffa M, Elwood RW, Dick JTA (1998) Analyses of repeated signals during hermit crab shell fights. Proc Roy Soc B 265:1467–1474
Broom DM (2007) Cognitive ability and sentience: which aquatic animals should be protected? Dis Aquat Org 75:99–108
Crump A, Browning H, Schnell A, Burn C, Birch J. (2022) Sentience in decapod crustaceans: A general framework and review of the evidence. Anim Sentience. https://doi.org/10.51291/2377-7478.1691
Doake S, Elwood RW (2011) How resource quality differentially affects motivation and ability to fight in hermit crabs. Proc Roy Soc B 278:567–573
Dowds BM, Elwood RW (1983) Shell wars: assessment strategies and the timing of decisions in hermit crab fights. Behaviour 85:1–24
Elwood RW (2012) Evidence for pain in decapod crustaceans. Anim Welf 21:23–27
Elwood RW (2019) Discrimination between nociceptive reflexes and more complex responses consistent with pain in crustaceans. Phil Trans Roy Soc B 374:20190368
Elwood RW (2022) Hermit crabs, shells, and sentience. Anim Cognit. https://doi.org/10.1007/s10071-022-01607-7
Elwood RW, Appel M (2009) Pain in hermit crabs? Anim Behav 77:1243–1246
Elwood RW, Arnott G (2012) Understanding how animals fight with Lloyd Morgan’s canon. Anim Behav 84:1095–1102
Elwood RW, Stewart A (1985) The timing of decisions during shell investigation by the hermit crab, Pagurus bernhardus. Anim Behav 33:620–627
Giurfa M, Zhang S, Jenett A et al (2001) The concepts of ‘sameness’ and ‘difference’ in an insect. Nature 410:930–933. https://doi.org/10.1038/35073582
Green PA (1871) Patek SN 2018 Mutual assessment during ritualized fighting in mantis shrimp (Stomatopoda). Proc Roy Soc b. 285:20172542. https://doi.org/10.1098/rspb.2017.2542
Jackson NW, Elwood RW (1989) How animals make assessments: information gathering by the hermit crab, Pagurus bernhardus. Anim Behav 38:951–957
Jackson NW, Elwood RW (1990) Interrupting an assessment process to probe changes in the motivational state. Anim Behav 39:1068–1077
Krieger J, Hörnig MK, Laidre ME (2020) Shells as ‘extended architecture’: to escape isolation, social hermit crabs choose shells with the right external architecture. Anim Cogn 23:1177–1187. https://doi.org/10.1007/s10071-020-01419-7
Lane SM, Brifa M (2020) The role of spatial accuracy and precision in hermit crab contests. Anim Behav 167:111–118. https://doi.org/10.1016/j.anbehav.2020.07.013
Leadbeater E, Chittka L (2008) Social transmission of nectar-robbing behaviour in bumble-bees. Proc Roy Soc B 275:1669–1674
Perry CJ, Chittka L (2019) How foresight might support the behavioral flexibility of arthropods. Curr Opin Neurobiol 54:171–177. https://doi.org/10.1016/j.conb.2018.10.014
Schnell AK, Smith CL, Hanlon RT, Harcourt R (2015) Giant Australian cuttlefish use mutual assessment to resolve male-male contests. Anim Behav 107:31–40
Sober E (2005) Comparative psychology meets evolutionary biology Morgan’s Canon and cladistic parsimony. In: Daston L, Mitman G (eds) Thinking with animals: new perspectives on anthropomorphism. Columbia University Press, New York, pp 85–99
Sonoda K, Asakura A, Minoura M, Elwood RW, Gunji P (2012) Hermit crabs perceive the extent of their virtual bodies. Biol Lett 8:495–497
Taylor P, Elwood RW (2003) Mis-measure of animal contests. Anim Behav 65:1195–1202
Acknowledgements
I am grateful to Ken Cheng, Mark Briffa and an anonymous referee for their excellent suggestions for improving this reply.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Conflict of interest
The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Ethical approval
Not applicable.
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Elwood, R.W. Caution is required when considering sentience in animals: a response to the commentary by Briffa (2022) on “Hermit crabs, shells, and sentience” (Elwood 2022). Anim Cogn 25, 1371–1374 (2022). https://doi.org/10.1007/s10071-022-01655-z
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10071-022-01655-z