From crabs to caterpillars, a wide range of animals successfully use camouflage to make detection by hungry predators more difficult. But some concealment strategies are more effective than others, a new study suggests.
The analysis compiles and synthesizes data from dozens of studies on animal camouflage. Comparisons between different camouflage methods show that posing as specific objects in the environment is the best way to go unnoticed, scientists report September 14 in Royal Society B Proceedings.
Behavioral and sensory ecologist João Vitor de Alcantara Viana had been studying animal camouflage for his doctoral research when he realized that a comprehensive comparison of different camouflage strategies had never been done.
“There was a huge gap in the literature on this topic,” says de Alcantara Viana, of the State University of Campinas in São Paulo, Brazil.
Therefore, De Alcantara Viana and colleagues searched databases of scientific publications for animal camouflage studies dating from 1900 to July 2022. The team zeroed in on 84 studies that experimentally tested at least one camouflage strategy. and reported how long it took predators to find camouflaged prey. or how often predators attack. The team also limited their analysis to studies that compared camouflaged prey with uncamouflaged, often artificial, versions.
Next, the team grouped the data from these studies according to the types of predators and prey analyzed and the variety of camouflage strategies examined. Camouflage tactics included “background matching,” where the animal matches the surrounding color and patternand “masked”, where the prey imitates a particular object that predators are not interested in, such as a twig, a leaf, a bird droppings or even a shedding tarantula skin (NS: 12/10/13; Serial number: 6/6/14).
Camouflage is generally effective at making it harder for predators to hunt, increasing their search time by more than 62 percent and reducing prey strike rate by more than 27 percent overall, the team found.
But the type of prey mattered. Caterpillars benefited more from camouflage than their winged adult forms, for example. This may be because moths and butterflies can fly and have other anti-predator adaptations available, says de Alcantara Viana.
The masking strategy was especially effective at helping prey evade predators, increasing search time by nearly 300 percent. One of the most striking examples of this, says de Alcantara Viana, are the caterpillars that disguise themselves as twigs. A study on the caterpillars of the sulfur moth (Opistographis luteolata) and chickens showed that birds take longer to attack masked caterpillars after recent exposure to twigs.
Impersonating the most effective camouflage strategy is intriguing, says Anna Hughes, a sensory ecologist at the University of Essex in England who was not involved in this research. “If this is indeed the case, it will be interesting to further investigate the limitations (size, movement requirements) that mean not all animals develop this strategy,” she says. The researchers note that masking is likely to evolve if the animal is similar in size to the object it is mimicking. This could limit which species can benefit from this super camouflage.
de Alcantara Viana and colleagues think that disguising is so effective because it is highly specialized, with animals posing as specific objects, compared to other strategies based on blending in with an irregular background. Prey that disguise themselves benefit from the predator misidentifying them as real objects in the environment, not just missing the prey.
The quality of the new work is excellent, says Hughes. Still, it’s not entirely clear whether uncamouflaged controls, which she says vary quite a bit from study to study, have inherently different effects on predator reactions. This could make the tested camouflage appear more or less effective than it is in the wild.
Another notable finding from the new analysis is that most of the studies have been conducted in the Northern Hemisphere, says Hughes. “I think it’s clear that our understanding of the evolution of camouflage strategies will, by definition, be incomplete unless further study is done in the southern hemisphere.”
Much of the recent camouflage research has also sought to understand precisely how specific defenses protect prey from attack, says Tom Sherratt, an evolutionary ecologist at Carleton University in Ottawa, Canada, who was also not involved in this study.
“We’re now at a point where we can start to compare these defenses,” Sherratt says, which may help researchers figure out why species use particular camouflage strategies.
de Alcantara Viana says he and his colleagues are working on another analysis to understand “the other side of the coin,” how camouflaged predators benefit by hiding from their prey.