AboutZoos, Since 2008


Medium-​sized car­ni­vores most at risk from envi­ron­men­tal change

pub­lished 06 Decem­ber 2017 | mod­i­fied 06 Decem­ber 2017

Aardwolves at Rare Species Conservation CentreIn a sur­prise eco­log­i­cal find­ing, researchers dis­cov­ered medium-​sized car­ni­vores spend the most time look­ing for food, mak­ing them vul­ner­a­ble to change.

Mam­malian preda­tors (com­monly called car­ni­vores) spend a sig­nif­i­cant part of their day for­ag­ing for food, and the more time they spend, the more energy they use. This makes preda­tors that spend a long time for­ag­ing more vul­ner­a­ble to changes in the envi­ron­ment that affect their pri­mary resource: their prey.

It had been thought that for­ag­ing time decreases as ani­mal size increases, but new research by Impe­r­ial Col­lege Lon­don and the Zoo­log­i­cal Soci­ety of Lon­don (ZSL) shows this is not the case.

The team used data on land preda­tors world­wide, from small preda­tors such as weasels to some of the largest such as tigers, to demon­strate that among all species, medium-​sized ones (between about one to ten kilo­grams in weight) spent the great­est part of their day for­ag­ing. Exam­ples of such medium-​sized car­ni­vores include the Malay civet, Iri­omote cat, Leop­ard cat, Crab-​eating fox and aardwolf.

The results, pub­lished on 4 Decem­ber in the jour­nal Nature Ecol­ogy & Evo­lu­tion, pro­vide meth­ods based on a new math­e­mat­i­cal model for pre­dict­ing the vul­ner­a­bil­ity of ani­mals to envi­ron­men­tal changes result­ing from habi­tat loss and cli­mate change.

Pre­dict­ing poten­tial risks
Study co-​author Dr Sam­raat Pawar, from the Depart­ment of Life Sci­ences at Impe­r­ial, said: “We pro­pose a sim­ple math­e­mat­i­cal model that pre­dicts how for­ag­ing time depends on body size. This can help pre­dict poten­tial risks to preda­tors fac­ing envi­ron­men­tal change. Habi­tat changes can mean that preda­tors have to move more to find the same amount of food, caus­ing them greater stress. This impacts the health of the indi­vid­ual, and there­fore the health of the pop­u­la­tion. Our approach could be used to bet­ter under­stand the diets of other groups of species as well improv­ing our knowl­edge of threats of cli­mate change and habi­tat loss in a wider range of species.”

Co-​author Mat­teo Riz­zuto, for­merly a Master’s stu­dent in the Depart­ment of Life Sci­ences at Impe­r­ial, noted that each species’ vul­ner­a­bil­ity will also depend on the kind of prey they feed on: “If they are able to adapt their diet and diver­sify their prey, they may fare better.”

Not enough bang for the buck
To test their the­ory about body size and for­ag­ing time, the team used car­ni­vore activ­ity data from across the world, col­lected through stud­ies using track­ing meth­ods such as radio col­lars and GPS. They looked at data from 73 land-​based car­ni­vore species.

The math­e­mat­i­cal model devel­oped by the team pin­points the rea­son why the sur­prise result might be so. Chris Car­bone, at ZSL, explained that for­ag­ing habits and the size-​difference between preda­tors and prey are likely the cause.

Medium-​sized preda­tors are forced to search for food for longer peri­ods of time on a daily basis because they tend to feed on prey that are small com­pared to their own size.

Dr Chris Car­bone, co-​author, Insti­tute of Zool­ogy, Zoo­log­i­cal Soci­ety of Lon­don, UK

Prey that are much smaller than a preda­tor are hard to find and catch, and there­fore do not eas­ily sat­isfy the predator’s energy needs and pro­vide insuf­fi­cient ‘bang for the buck’,” Car­bone adds.

(Source: Impe­r­ial Col­lege Lon­don news release, 04.12.2017)

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