Now, fish in­cluded in pray­ing man­tid menu

Fish-eat­ing be­hav­iour has not been seen un­til now

The Hindu - - SCIENCE & TECHNOLOGY - Aathira Per­inch­ery

Pray­ing man­tids prey on smaller in­sects and some­times the odd frog or lizard. Now, it looks like they’ve added fish to their menu too, for nat­u­ral­ists have ob­served one catch­ing and eat­ing small or­na­men­tal fish in a gar­den in Ben­galuru.

Guppy-catcher

It was on the evening of March 7 last year that nat­u­ral­ist Ra­jesh Put­taswa­ma­iah's young son Arya came run­ning to him at his home in Ben­galuru, up­set that “some spi­der-like in­sect” was catch­ing his prized gup­pies. A cu­ri­ous Put­taswa­ma­iah went to his first-floor ter­race gar­den, where his large earth­en­ware planter dou­bles as a mini-pond, re­plete with wa­ter lilies, wa­ter cab­bage and small or­na­men­tal fish in­clud­ing gup­pies, ze­brafish and molly fish.

What he saw was ex­tremely in­trigu­ing: an al­most six cen­time­tre­large pray­ing man­tid of the species

Hiero­dula tenuiden­tata

was feasting on a freshly-caught guppy. A few hours later, Put­taswa­ma­iah and his son ob­served the man­tid catch yet an­other guppy.

They ob­served this for four more days: the man­tid would ap­pear at around dusk, fish gup­pies out of the wa­ter and promptly eat them. Over five days, it ate nine male gup­pies out of the 40 fish in the planter. Such fish­ing or fish-eat­ing be­hav­iour has never been recorded be­fore in pray­ing man­tids, and Put­taswa­ma­iah and his team re­ported it in the

Jour­nal of Orthoptera Re­search

re­cently. “The man­tid’s be­hav­iour raises many ques­tions,” says Put­taswa­ma­iah.

Adap­ta­tions

The com­pound eyes of most man­tids are adapted to day­light, but here was one that man­aged to hunt fast-mov­ing prey – gup­pies – in very low light. More­over, the in­sect was able to over­come the re­frac­tion of light in wa­ter (when light trav­els into wa­ter, it slows down, thereby chang­ing di­rec­tion slightly) which makes it dif­fi­cult for a ter­res­trial preda­tor to catch an aquatic crea­ture.

Put­taswa­ma­iah and his co-au­thors ar­gue that the re­peated pre­da­tion also sug­gests that man­tids could learn new hunt­ing strate­gies from ex­pe­ri­ence and dif­fer­ent en­vi­ron­men­tal cues.

How­ever, while the ob­ser­va­tion is in­ter­est­ing, it would be safer to say that man­tids have ex­cel­lent vi­sion and are now known to at­tack mov­ing prey un­der wa­ter ac­cord­ing to Divya Uma, a pro­fes­sor at the Azim Premji Univer­sity who stud­ies in­sects in­clud­ing man­tids.

“Man­tids at­tack any mov­ing ob­ject of a par­tic­u­lar size,” she wrote in an email. “Man­tids (and all in­sects) can learn, re­mem­ber and mod­ify their be­hav­iour based on ex­pe­ri­ence. A strike to­wards a mov­ing prey is an in­nate re­sponse.”

RA­JESH PUT­TASWA­MA­IAH ■

Vo­ra­cious: Over five days, the ob­served man­tid ate nine male gup­pies out of the 40 fish in the planter.

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