Frogs ex­posed to deadly virus breed younger

Western Morning News (Saturday) - - Uk And World News - BY CLAIRE HAYHURST

Frogs from groups ex­posed to a deadly virus are breed­ing at younger ages than those free from the disease, re­search sug­gests.

Sci­en­tists found the youngest breed­ing frogs in pop­u­la­tions af­fected by ranavirus were aged two, while those in disease-free ar­eas bred from the age of four.

The team, led by researchers at the Univer­sity of Ex­eter and ZSL’s In­sti­tute of Zo­ol­ogy, warn this de­crease in breed­ing age means disease-ex- posed pop­u­la­tions are at greater risk of lo­cal ex­tinc­tion from en­vi­ron­men­tal changes.

Frogs gather at breed­ing spots such as ponds and then dis­perse, with most re­turn­ing to the same ponds year af­ter year.

Dr Lewis Camp­bell, who con­ducted the re­search dur­ing his PhD at the Univer­sity of Ex­eter, said: “We found sig­nif­i­cantly fewer old frogs and sig­nif­i­cantly more young frogs at pop­u­la­tions which have ranavirus.

“It’s pos­si­ble that the more times an older frog re­turns to the same in­fected breed­ing pond, the more likely they are to be­come dis­eased and die.

“The ab­sence of older frogs may then cre­ate an op­por­tu­nity for younger – and there­fore smaller and less com­pet­i­tive – frogs to suc­cess­fully breed.

“With high mor­tal­ity among older frogs, it’s also pos­si­ble that nat­u­ral se­lec­tion pres­sure has favoured those that are ge­net­i­cally disposed to breed younger.”

Ranavirus, which was first recorded in the UK in the 1980s and is usu­ally fa­tal, can cause se­vere skin sores and in­ter­nal bleed­ing. In the study, which in­cor­po­rated data col­lected by ci­ti­zen sci­en­tists, breed­ing frogs in disease-free pop­u­la­tions were usu­ally aged be­tween six to eight years old.

But those in pop­u­la­tions where ranavirus was present were mostly aged three to six years old.

Dr Camp­bell, now of the Univer­sity of Wis­con­sinMadi­son, said: “Disease-ex­posed pop­u­la­tions ap­pear to de­pend heav­ily on younger breed­ers that don’t pro­duce as many off­spring.”

PA

Frogs gather at breed­ing spots such as ponds and then dis­perse

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