Know your salamander: To conserve amphibians, study their intelligence (commentary)

By Deyatima Ghosh

After years of questioning, skepticism and denial, we are finally ready to embrace the beauty of the animal mind.

Primates have contributed enormously to the understanding of mental abilities mostly for their “human-like” behaviors or close links to humans which made ethologists keen to study cognition in other animals such as birds, reptiles, amphibians, fishes as well as invertebrates such as cephalopods. Although, initially, cognition has been compared on a single scale where humans occupy the top tier and moves downwards to other mammals, the more we started discarding our human standards of understanding capacities in animals, the more the scale was broken into bushes with several branches. Each such branch is unique and is occupied by a group of animals that expresses mental capabilities at their finest level.

Salamanders are of interest, and here’s why

Amphibians occupy one such branch which is least explored. Among the amphibians, Caudata, including salamanders, still remain a mystery at large. The etymology comes from Greek which means “fire lizard.” Salamanders, which occur in North America, Europe, Asia, northern parts of South America and north Africa, resemble lizards without scales. Around 60% of salamander species are threatened with extinction and are in urgent need of conservation.

A California tiger salamander, which is listed as ‘Vulnerable’ on the IUCN Red List. Around 60% of salamander species are threatened with extinction and are in urgent need of conservation. Image by Natalie McNear via Flickr (CC BY-NC 2.0).

What do we know about salamander’s mental capabilities?

Number discrimination

Salamanders are least studied for their cognitive abilities. They have been tested for their ability to discriminate between numbers. Being able to differentiate between more or less can influence decision-making regarding foraging, mating, and avoiding predators. Although the numeric system in salamanders is limited, they have the precision to track small numerals and individuals can discriminate between numbers spontaneously.

There is debate on the method salamanders use to discriminate between quantity. With larger numerals such as 3 vs. 4 or 4 vs. 6, salamanders do not discriminate between more or less. This could be because comparing more and fewer matters only when the resource is limited. But with enough resources, e.g., 4 vs. 6 choosing more from big quantities doesn’t add value as much as choosing 2 vs. 1 would do.

To date, we are not yet able to decipher the underlying reasoning for numeric capacities in salamanders. That salamanders understand number system is clear from the optimum foraging strategy in red-backed salamanders (Plethodon cinereus), which choose the larger-sized flies when the prey number is more. However, at smaller prey number, they do not discriminate between the size of prey. This ability to decide and modify foraging is possible only because they inherently possess a number system.

Quantity discrimination is essential for survival. It allows animals to choose between groups, increase probability of encountering mates, avoid predators and choose foraging sites. The ability to understand number in this basal group of animals can provide clues regarding the evolution of the number system in other animals including us humans and, surely, such abilities are not limited to humans.

Red-backed salamanders were observed to choose the larger-sized flies when the prey number is more. However, at smaller prey number, they do not discriminate between the size of prey. Image by Grigory Heaton via Flickr (CC BY-NC 2.0).

Memory

Memory plays an essential role in the survival of animals where individuals can draw a memory to execute a task in the wild. What is more interesting among salamanders is the hibernation of the larvae during which their synaptic activity is reduced. This can cause them to lose some of the memories they formed prior to hibernation, due to a negative impact on neuronal connections.

It is important to have memory of past events such as the location of food, threats from predators and social information which can improve chances of survival post-metamorphosis. The processes in hibernation vary between warm- and cold-blooded animals. While hibernating, mammals lose 50-65% of synapses, experiencing periods of arousal and sleep, which positively affects brain cells. In contrast, salamanders experience very low temperatures and are forced to stay torpid until temperatures rise. Hibernation is responsible for significant changes in hippocampal connectivity. Rapid cooling of temperature prevents new synthesis of proteins which are required to form long-term memory, and cell death in the cerebral hemispheres in cold temperature has been recorded. We do not know how much synapsis is lost during hibernation and the rapidity of re-growing the synaptic connections when the temperature becomes favorable. Salamanders experience drastic changes in temperature in early life and, often, the larval period is extended for years.

Remarkably, salamanders can retain memory post brumation. Since retention of memory is adaptive and improves survival, it should be selected by nature. Having memory can allow them to return to rewarding foraging sites or secured shelter without spending time and energy in prospecting the habitat. It can further enable salamanders to remember the reproductive sites as species such as the giant salamanders (Andrias sp.) use a den called “den masters” to lay their eggs and provide parental care.

Learning

Salamanders have been shown to learn and remember patterns. They can learn to use landmarks (i.e. beacon homing) to find foraging patches as seen in Ozark zigzag salamanders (Plethodon angusticlavius). Terrestrial salamanders can maintain above-ground site-specific territories for several months, with some territories re-occupied by the same individuals even after an over-wintering period when salamanders occupy underground burrows. Past research suggests that salamanders have the ability to learn using visual cues to navigate a maze. Additionally, they learn to use feature and geometric cues to navigate. Learning actually starts much before in life as early as an embryonic stage where embryos can be cued to novel food through olfaction.

Olfaction

Olfactory organs differ in size, shape, and distribution of olfactory tissues depending on habitat type during the post-metamorphic stages as seen in Salamandridae family. Male red-backed salamanders were studied to determine the origin of the chemical cues allowing for individual odor recognition between conspecifics. Individual male red-backed salamanders show a preference for substrates with their own fecal and cloacal odors rather than those marked by unfamiliar conspecific males.

Tiger salamander (Ambystoma tigrinum) larvae. Salamanders experience drastic changes in temperature in early life and, often, the larval period is extended for years. Image by Andrey Zharkikh via Wikimedia Commonslarvae,Utah.jpg) (CC BY 2.0).

A lot more awaits our understanding

Salamanders possess number system and memory post hibernation, and they show evidence of self-recognition, spatial reward learning and associating color with reward. Despite having a relatively simple brain structure, salamanders are capable of complex cognition.

The cryptic nature of the group has added to the limited knowledge about their habitat, ecology, reproductive biology, behavior and, most of all, cognition. Knowing less about these animals also results in uninformed conservation planning that often doesn’t reach satisfactory outcomes. With many species of salamander endangered, more studies are required to fully unravel the mysteries hidden by this group of amphibians and their implications in conserving them in the wild.

Conservation biologists therefore need to change the way they look at conservation and explore potential avenues to utilize cognition abilities to improve conservation. Numeric abilities can be used to attract salamanders towards a specific site within habitats by supplementing sites with more shelter, decoys or even supplementary food.

Because of their ability to use features and geometric cues to navigate, introducing such elements in the habitat can attract the species towards a rewarding foraging patch or a rewarding mating area, even a potential site to avoid predators. For the same reason, areas where individuals occur originally should not be altered as this might disrupt memory formation or prevent the animals from using the already learned information to navigate in their habitat.

Additionally, olfactory discrimination can be used to alter the animal’s choice of occupying sites such as using heterospecific odor prepared from the fecal matter spread on leaves and stones or other objects that the animals regularly come across. Similarly, predator odor can be used to prevent animals from frequenting risky sites while increasing their occurrence in safe places. This learning can be enhanced by adding conspecific odor or odor of from the same individuals.

There is definitely potential in exploring salamander cognition as an avenue to improve or complement conservation strategies. Success with this paradigm can offer the potential in future studies to delve deeper into an animal’s cognition further, as well as to shed light on how cognition can be harnessed as a major strategy in conservation.

Banner image: A fire salamander, vulnerable on the IUCN list. Image by Paweł Sroka via Unsplash (Public domain).

Cittions:

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Jaeger, Robert G., and Debra E. Barnard. “Foraging Tactics of a Terrestrial Salamander: Choice of Diet in Structurally Simple Environments.” The American Naturalist, vol. 117, no. 5, 1981, pp. 639–64. JSTOR, http://www.jstor.org/stable/2460751.

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This article was originally published on Mongabay