Smart sharks: a review of chondrichthyan cognition

Abstract

Abstract450 million years of evolution have given chondrichthyans (sharks, rays and allies) ample time to adapt perfectly to their respective everyday life challenges and cognitive abilities have played an important part in that process. The diversity of niches that sharks and rays occupy corresponds to matching diversity in brains and behaviour, but we have only scratched the surface in terms of investigating cognition in this important group of animals. The handful of species that have been cognitively assessed in some detail over the last decade have provided enough data to safely conclude that sharks and rays are cognitively on par with most other vertebrates, including mammals and birds. Experiments in the lab as well as in the wild pose their own unique challenges, mainly due to the handling and maintenance of these animals as well as controlling environmental conditions and elimination of confounding factors. Nonetheless, significant advancements have been obtained in the fields of spatial and social cognition, discrimination learning, memory retention as well as several others. Most studies have focused on behaviour and the underlying neural substrates involved in cognitive information processing are still largely unknown. Our understanding of shark cognition has multiple practical benefits for welfare and conservation management but there are obvious gaps in our knowledge. Like most marine animals, sharks and rays face multiple threats. The effects of climate change, pollution and resulting ecosystem changes on the cognitive abilities of sharks and stingrays remain poorly investigated and we can only speculate what the likely impacts might be based on research on bony fishes. Lastly, sharks still suffer from their bad reputation as mindless killers and are heavily targeted by commercial fishing operations for their fins. This public relations issue clouds people’s expectations of shark intelligence and is a serious impediment to their conservation. In the light of the fascinating results presented here, it seems obvious that the general perception of sharks and rays as well as their status as sentient, cognitive animals, needs to be urgently revisited.

Perceptions regarding the recreational cobia fishery in relation to manta ray conservation

“…Research into manta social behaviour and capacity to learn may support the feasibility of this claim (Perryman et al, 2019). Chondrichthyan species have complex learning capabilities, although the extent of these capabilities is still poorly understood due to difficulties in handling and maintaining many species of sharks and rays in captive or semi‐captive environments (Brown & Schluessel, 2023; Guttridge et al, 2009). Thus, it is reasonable to assume that manta rays have the potential to learn to avoid boats in the area to avoid accidental hooking, boat strikes or harassment.…”

Inhibitory control in teleost fish: a methodological and conceptual review

“…A positive example is the study of sex differences, involving at least six teleost species to date. It is noteworthy that, to the best of my knowledge, the literature lacks studies on cartilaginous fish, even if this group garners increasing attention for other cognitive abilities (reviewed in Brown and Schluessel 2023 ).…”

Operant conditioning as a tool to assess hearing abilities in sharks

“…Hearing is a cognitive process that requires more than the detection of sound by receptor cells and the transmission of electrical signals via neural pathways to the brain (Popper & Hawkins, 2021). It also involves the interpretation of auditory information, which the animal uses to locate and respond to resources or threats (Brown & Schluessel, 2022). Typically, hearing abilities in fish are assessed using physiological approaches (Ladich & Fay, 2013), which are indirect measures of hearing, as they do not require the integration of acoustic signals at the whole‐animal level (Popper et al ., 2019).…”

“…Sharks have the capacity to learn and can solve cognitive tasks (Brown & Schluessel, 2022; Guttridge et al ., 2009; Guttridge et al ., 2018; Schluessel, 2015). Hearing is a cognitive process that requires more than the detection of sound by receptor cells and the transmission of electrical signals via neural pathways to the brain (Popper & Hawkins, 2021).…”