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Hunt­ing accounts for mas­sive declines in trop­i­cal ani­mal populations

pub­lished 15 April 2017 | mod­i­fied 15 April 2017

Hunt­ing is a major threat to wildlife par­tic­u­larly in trop­i­cal regions, but a sys­tem­atic large-​scale esti­mate of hunting-​induced declines of ani­mal num­bers was lack­ing so far. A study pub­lished on 14 April in the jour­nal Sci­ence fills this gap. A team of ecol­o­gists and envi­ron­men­tal sci­en­tists found that bird pop­u­la­tions declined on aver­age by 58 per­cent and mam­mal pop­u­la­tions by 83 within 7 and 40 km of hunters’ access points, such as roads and settlements.

Addi­tion­ally, the team found that com­mer­cial hunt­ing had a higher impact than hunt­ing for fam­ily food, and that hunt­ing pres­sure was higher in areas with bet­ter acces­si­bil­ity to major towns where wild meat could be traded. The impact of hunt­ing was found to be larger than the team expected. ‘Thanks to this study, we know that only 17 per­cent of the orig­i­nal mam­mal abun­dance and 42 per­cent of the birds remain in hunted areas.’

The researchers syn­the­sised 176 stud­ies to quan­tify hunting-​induced declines of mam­mal and bird pop­u­la­tions across the trop­ics of Cen­tral and South Amer­ica, Africa and Asia. The team, led by Ana Benítez-​López from the Rad­boud Uni­ver­sity in Nijmegen, com­prised researchers from the Nether­lands Envi­ron­men­tal Assess­ment Agency (PBL), the uni­ver­si­ties of Wagenin­gen and Utrecht in the Nether­lands and from the Uni­ver­sity of Sussex.

DefaunationInfo­graphic of the impact of hunt­ing on trop­i­cal mam­mal and bird pop­u­la­tions,
Image credit Rad­boud Uni­ver­sity
Benítez-​López et al., 2017. The impact of hunt­ing on trop­i­cal mam­mal and bird pop­u­la­tions in Science.

Higher hunt­ing pres­sure around vil­lages and roads
’There are sev­eral dri­vers of ani­mal decline in trop­i­cal land­scapes: habi­tat destruc­tion, over­hunt­ing, frag­men­ta­tion etcetera. While defor­esta­tion and habi­tat loss can be mon­i­tored using remote sens­ing, hunt­ing can only be tracked on the ground. We wanted to find a sys­tem­atic and con­sis­tent way to esti­mate the impact of hunt­ing across the trop­ics. As a start­ing point, we used the hypoth­e­sis that humans gather resources in a cir­cle around their vil­lage and in the prox­im­ity of roads. As such, hunt­ing pres­sure is higher in the prox­im­ity of vil­lages and other access points. From there the den­si­ties of species increase up to a dis­tance where no effect of hunt­ing is observed. We called this species deple­tion dis­tances which we quan­ti­fied in our analy­sis. This will allow us to map hunting-​induced declines across the trop­ics for the first time,’ Benítez-​López explains.

Strate­gies to sus­tain­ably man­age wild meat hunt­ing in both pro­tected and unpro­tected trop­i­cal ecosys­tems are urgently needed to avoid fur­ther defaunation
Ana Benítez-​López, depart­ment of Envi­ron­men­tal Sci­ence, Rad­boud Uni­ver­sity, Nijmegen, The Netherlands »

Not only the big cud­dly species
The main nov­elty of the cur­rent study is that it com­bined the evi­dence across many local stud­ies, thus for the first time pro­vid­ing an over­ar­ch­ing pic­ture of the mag­ni­tude of the impact across a large num­ber of species. The study takes all ani­mals into account — not only the big cud­dly species, but birds and rodents as well. Benítez-​López explains the dif­fer­ence in impact between birds and mam­mals: ‘Mam­mals are more sought after because they’re big­ger and pro­vide more food. They are worth a longer trip. The big­ger the mam­mal, the fur­ther a hunter would walk to catch it.’

With increas­ing wild meat demand for rural and urban sup­ply, hunters have har­vested the larger species almost to extinc­tion in the prox­im­ity of the vil­lages and they must travel fur­ther dis­tances to hunt. Besides, for com­mer­cially inter­est­ing species such as ele­phants and goril­las, hunt­ing dis­tances are much larger because the returns are higher.

Pro­tected areas are no safe haven
Another inter­est­ing find­ing of this study is that mam­mal pop­u­la­tions have also been reduced by hunt­ing even within pro­tected areas. ‘Strate­gies to sus­tain­ably man­age wild meat hunt­ing in both pro­tected and unpro­tected trop­i­cal ecosys­tems are urgently needed to avoid fur­ther defau­na­tion,’ she says. ‘This includes mon­i­tor­ing hunt­ing activ­i­ties by increas­ing anti-​poaching patrols and con­trol­ling over­ex­ploita­tion via law enforcement’.

(Source: Rad­boud Uni­ver­sity news release, 13.04.2017)

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