Live fast die young: Updating signal detection theory

October 18, 2017, UC Davis
Credit: CC0 Public Domain

Signal Detection Theory is a popular and well-established idea that has influenced behavioral science for around 50 years. Essentially, the theory holds that in a predator-prey relationship, prey animals will show more wariness and be more prone to flee as predators become more common. Danger signals are ambiguous, so in what appears to be a threatening situation, animals are better off running than hanging around to see if a predator really does strike.

Now Pete Trimmer, a postdoctoral research at UC Davis, has taken a fresh look at signal detection and come up with what at first look like counterintuitive results. In many cases, he says, should actually become less cautious as the risk of predation rises.

The problem with conventional signal detection theory, Trimmer says, is that it only considers one decision at a time, in isolation. But in reality, animals may have to make multiple connected decisions and have to take into account the effects of decisions over time.

Trimmer, graduate student Sean Ehlman and Professor Andy Sih at UC Davis, with mathematician John McNamara at the University of Bristol, U.K. developed a that they call state-dependent detection theory or SDDT. The work is published Oct. 18 in the journal Proceedings of the Royal Society B.

A browsing animal detects that a may be near. Keep feeding or flee? Conventional theory only considers that decision. But what if the animal is near starvation? Fleeing too soon might save its life in the short term, but it might die of hunger later.

The new theory takes those factors into account by setting a threshold that depends on the energy "reserves" of the prey. When an animal's reserves are high, it can afford to miss a feeding opportunity and is more likely to flee but if it is hungry, it is more likely to stay.

More Predators, Less Caution

State-Dependent Detection Theory generates another surprise result: Trimmer and colleagues found that as the probability of danger rises, the threshold to flee actually goes up so animals will tolerate higher danger signals before fleeing.

But on second look, there's sound logic to this, Trimmer says. When your overall risk of dying on the claws of a predator is high, your life is going to be shorter and your reproductive success less. So the payoff for any single time that you flee is lower: you're just postponing the risk to a later time. You might as well take the risks, live fast and die young.

"Put another way, if predators are rare, when an organism receives a signal of possible danger, it can afford to flee because it should have plenty of opportunity to make up for lost energy at a later time. In contrast, if predators are very common, the organism cannot afford to flee everytime it receives a signal of possible danger," the authors write.

The new model could have wide implications, from how careful animals are about possibly toxic foods to how easily the immune system is triggered by an infection or allergy. It could also help in understanding animal welfare: an animal that is generally comfortable might show more alarm in response to some signal than an animal that is more stressed overall.

Explore further: Marine plants can flee to avoid predators, researchers say

More information: The erroneous signals of detection theory, Proceedings of the Royal Society B, rspb.royalsocietypublishing.or … .1098/rspb.2017.1852

Related Stories

Marine plants can flee to avoid predators, researchers say

September 28, 2012

Scientists at the University of Rhode Island's Graduate School of Oceanography have made the first observation of a predator avoidance behavior by a species of phytoplankton, a microscopic marine plant. Susanne Menden-Deuer, ...

Island monkeys do not recognize big cat calls

January 17, 2008

Monkeys living on an island without big cat predators do not show any particular alarm when recorded tiger growls are played to them, according to research by a UC Davis graduate student. The pig-tailed langurs do, however, ...

Recommended for you

A world of parasites

May 25, 2018

Alex Betts, Craig MacLean and Kayla King from the Department of Zoology, shed light on their recent research published in Science, which addressed the impact that parasite communities have on evolutionary change and diversity.

Bumblebees confused by iridescent colors

May 25, 2018

Iridescence is a form of structural colour which uses regular repeating nanostructures to reflect light at slightly different angles, causing a colour-change effect.

A better B1 building block

May 25, 2018

Humans aren't the only earth-bound organisms that need to take their vitamins. Thiamine – commonly known as vitamin B1 – is vital to the survival of most every living thing on earth. But the average bacterium or plant ...

Plant symbioses—fragile partnerships

May 25, 2018

All plants require an adequate supply of inorganic nutrients, such as fixed nitrogen (usually in the form of ammonia or nitrate), for growth. A special group of flowering plants thus depends on close symbiotic relationships ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.