Large predators can mitigate nutrient losses associated with off‐site removal of animals from a wildlife reserve. Issue 7 (23rd April 2021)

• Record Type: Journal Article
• Authors: Abraham, Andrew J.; Webster, Andrea B.; Prys‐Jones, Tomos O.; le Roux, Elizabeth; Smith, Dylan; McFayden, Duncan; de Jager, Pieter C.; Clauss, Marcus; Doughty, Christopher E.
• Is Part Of: Journal of applied ecology. Volume 58:Issue 7(2021)
• Page Start: 1360
• Page End: 1369
• Publication Date: 2021-04-23
• Subjects: biogeochemistry -- calcium -- carnivore -- nutrient cycles -- phosphorus -- skeleton -- wildlife management; Agriculture -- Periodicals; Biology, Economic -- Periodicals; Agricultural ecology -- Periodicals; Applied ecology -- Periodicals; 577
• DOI: 10.1111/1365-2664.13878
• Languages: English
• ISSNs: 0021-8901

Abstract

Abstract: Animals concentrate key nutrients in their bodies. In fenced wildlife reserves where nutrient input and/or retention is low, the off‐site removal of animals may constitute a significant loss of nutrients for the ecosystem. Here we add wildlife capture and removal into the phosphorus (P) and calcium (Ca) budget for a 121, 700 ha fenced game reserve located in the southern Kalahari. We then use faecal P concentrations from 11 mammal herbivores >10 kg as an indicator of potential nutrient stress in this system to investigate whether the implications of nutrient loss via off‐site wildlife removal may be cause for concern. Finally, we assess the role of natural predation as a mechanism to minimise the need for wildlife removal and concomitant nutrient loss. During the period 2009–2018, mean loss of P and Ca via wildlife removal was 2.9 and 6.2 kg km −2 year −1, respectively. This compares to 1.0 and 2.1 kg km −2 year −1 of P and Ca added via the provision of mineral licks. If it is assumed that natural fluxes of these elements are in steady state, then anthropogenic activities have resulted in a net deficit of 18.5 kg/km 2 of P and 40.6 kg/km 2 of Ca over the decade. We found that dry season herbivore faecal P concentrations are close to or below a widely cited minimum threshold of 2, 000 mg/kg, below which most vertebrates begin suffering growth and reproductive issues. Large animals were more likely to be under this threshold. Prolonged continuation of off‐site wildlife removal may result in nutrient losses that can lead to long‐term ecological degradation. Natural predation levels were, however, found sufficient to mitigate the need for wildlife removal and present a management strategy whereby herbivore populations can be regulated without a loss of nutrients. Synthesis and applications . We find that the capture and permanent removal of large‐bodied animals from wildlife reserves can be a significant cause of nutrient loss. Over time, in sites where nutrient input and/or retention is low, this may contribute to nutritional stress for remaining resident animals. Where possible, holistic management strategies that promote the retention of animals and carcasses within the reserve—such as the reintroduction of large carnivores—should be preferred. Abstract : We find that the capture and permanent removal of large‐bodied animals from wildlife reserves can be a significant cause of nutrient loss. Over time, in sites where nutrient input and/or retention is low, this may contribute to nutritional stress for remaining resident animals. Where possible, holistic management strategies that promote the retention of animals and carcasses within the reserve—such as the reintroduction of large carnivores—should be preferred. Isicatshulwa: Izilwanyana ziqokelela ndawonye izondlo ezingundoqo emizimbeni yazo. Kwithanga elibiyelweyo lokugcina izilwanyana zasendle apho igalelo lezondlo okanye ukugcinwa kwezondlo kuphantsi, ukususwa ngaphandle kwethanga kwezilwanyana kusenokwenza ilahleko ebalulekileyo yezondlo kwindalo. Apha sidibanisa ukubanjwa nokususwa kwezilwanyana zasendle kumyinge we‐ phosphorus (P) kunye necalcium (Ca) kwithanga lwezilwanyana zasendle elinesiza esiyi 121, 700 ha elifumaneka emazantsi eKalahari. Sisebenzise ke iphosphorus efumaneka ebulongweni bezilwanyana ezanyisayo ezilishumi elinanye, ezibunzima bungaphezulu kweshumi lwekilograms njengesalathisi soxinizelelo lwezondlo olunokubakho koluhlobo lwethanga xa besiphanda ukuba ukuchaphazeleka koxinizelelo lwezondlo ngenxa yokususwa ngaphandle kwethanga kwezilwanyana kunokuba ngunobangela wenkxalabo. Okokugqibela, sivavanya indima yokutyiwa kwezilwanyana zezinye njengesixhobo esingasetyenziswa ukunciphisa isidingo sokususwa kwezilwanyana zasendle kumathanga wazo ehambelana kunye nokulahleka kwezondlo. Ngexesha lika 2009 ukuya kunyaka ka 2018, ilahleko yephosphorus necalcium ngenxa yokususwa kwezilwanyana zasendle kumathanga wazo ibingumlinganiselo ongangesithathu (2.9 kg km −2 year −1 ) kwiphosphorus nesithandathu (6.2 kg km −2 year −1 ) kwicalcium. Oku kuthelekiswa kumlinganiselo omnye (1.0 kg km −2 year −1 ) wephosphorus kunye nemibini (2.1 kg km −2 year −1 ) yecalcium ezongezwe lubonelelo lweemitha zezimbiwa. Ukuba kucingelwa ngaba ukubhobhoza ngokwendalo kwezizinto kukwimeko ezinzileyo, ithetha ukuthi lonto imisebenzi eyenziwa ngabantu ephazamisa indalo ibangele intsilelo eninzi, engumlinganiselo weshumi elinethoba (18.5 kg/km 2 ) lwephosphorus namashumi amane ananye ecalcium (40. 6 kg/km 2 ) kwiminyaka elishumi. SIfumanise ukuba iphosphorus kubulongwe bezilwanyana ezanyisayo obuqokelelwe ngexesha lonyaka ekome ngalo isondele okanye ingezantsi kumyinge obekiweyo ngokubanzi wamawaka amabini (2, 000 mg/kg), myinge lowo ongezantsi othi wenze uninzi lwezilwanyana ezinomqolo ziqale ukukhula ngokubandezeleka kuchaphazeleke nemicimbi yokuzala. Izilwanyana ezinkulu bekusenzeka ukuba zibengezantsi kwalomyinge. Ukuqhubeka ixesha elide kokususwa kwezilwanyana zasendle kumathanga wazo kunobangela ilahleko yezondlo engakhokelela ekonakaleni kwendalo ixesha elide. Nangona kunjalo amanqanaba okutyiwa kwezilwanyana zezinye afunyenwe onele ukunciphisa isidingo sokususwa kwezilwanyana zasendle kumathanga wazo kwaye ivelisa iqhinga lolawulo apho izilwanyana zinokulawulwa ngaphandle kokulahleka kwezondlo. Indibanisela noncedo: Sifumanisa ukuba ukubanjwa nokususwa ngokusisigxina kwezilwanyana zasendle kumathanga wazo kunokuba ngunobangela wokulahleka kwezondlo. Emva kwexesha elide, emathangeni apho igalelo okanye ukugcinwa kwezondlo kuphantsi kungenza uxinizelelo lwezondlo kwizilwanyana ezishiyekileyo. Apho kunokwenzeka, izicwangciso zolawulo olubanzi olukhuthaza ukugcinwa kwezilwanyana kunye nezidumbu ngaphakathi emathangeni ‐ njengokungeniswa kwakhona kwezilwanyana ezitya ezinye‐ kokona kufanele kukhethwe.