Reproduction and behaviour of the endangered European mink (Mustela lutreola) in captivity
Date
2017-12-20
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Abstract
Euroopa naarits on kriitiliselt ohustatud imetaja, mis on loodusest kadumas. Päästmaks liiki väljasuremisest hakati naaritsaid pidama loomaaedades. Vangistuses on loomade paljundamine keeruline, kuna sealne keskkond erineb looma looduslikust elupaigast. Loomaaias elavatel naaritsatel on täheldatud probleeme sigimisega. Paljud ei saa järglasi, mis võib saada saatuslikuks asurkonna jätkusuutlikkusele.
Käesolevas doktoritöös uurisin, miks on naaritsa sigimine loomaaias ebaedukas ja kuidas leida probleemile lahendus. Olukorrast parema ülevaate saamiseks uurisime, mis mõjutab pesakonna suurust ja poegade tõenäosust ellu jääda. Leidsime, et olulised on ema vanus ja kaal, kuid muidu oli emaste sigimisedu sarnane. Lisaks uurisime emase hormonaaltsüklit indlemise ja tiinuse ajal. Tulemused olid ootuspärased, hormonaaltsükkel järgis liigile tüüpilist rada.
Me ei leidnud tõendeid, et paaritamiskatsete ebaõnnestumise põhjust tuleks otsida emastest. Leidsime, et ebaedu sigimisel on seotud vangistuses sündinud isastega. Mõni isane on paaritamiskatses emase vastu agressiivne või siis neil puudub indleva emase vastu huvi. Mõistmaks isaste käitumist vaatlesime naaritsate lapsepõlve – uurisime poegade vahelisi suhteid pesakonnas kasvamise ajal. Paljudel imetajatel on tõendatud, et varajane keskkond mõjutab isendi käitumist täiskasvanueas. Me ei leidnud, et naaritsatel oleks pesakonnaperioodil ebanormaalset käitumist. Nagu igati kohane, kulus poegade põhiaeg mängule. Agressiivsust ei olnud palju ja see ei tõusnud ajas. Pesakonnad ei erinenud käitumismustrilt üksteisest, seega ei leidnud me hälbiva poegade käitumisega pesakondi, mis oleksid võinud ebasobiva sigimiskäitumise tekkimist seletada.
Töötasime välja metoodika naartisate iseloomutüüpide määramiseks, sest üha enam soovitatakse, et loomadesse tuleks loomaaias suhtuda neist igaühe iseloomu arvestades. Leidsime, et naaritsaid saab eristada julguse, uurivuse ja sotsiaalsuse alusel .
Meie töös ilmnes, et probleemid sigimishooajal on seotud eelkõige vangistuses sündinud isastega, nende põhjuseid peaks otsima mujalt kui pesakonnaperioodist, abi võiks olla iga looma iseloomu tundmisest. Saadud tulemused on oluliseks alusteadmisteks töös, mis on suunatud naaritsate tehiskeskkonnas pidamise edukuse tõstmisele.
European mink is a critically endangered carnivore which has almost disappeared from nature. To save the species from extinction a captive population was established. Unfortunately, keeping wild animals in captivity always causes problems, just because in a zoo everything is different from the species’ natural habitat. In the case of the European mink, there are problems with breeding in captive conditions. Some animals will fail to produce offspring which may threaten the persistence of the captive population. In this doctorial thesis, I addressed the reasons of breeding failures and how to find solutions to this problem. At first we studied what affects the size and survival of the litter. We found that the weight and age of the mother are most significant. Additionally we studied the hormonal cycle of the females during the mating season and gestation. Results were expectable: the hormonal cycle followed a profile typical of the species. Analysing the diaries kept at Tallinn zoo for 20 years, we did not find that something is wrong on the females’ side. Instead, we found that the breeding problems are caused by males which have been born in captivity. Some males are aggressive toward the female during the mating attempt or remain passive. To understand the reasons for kind of behaviour, we focused on the childhood of the mink: we studied the interactions between the cubs during the litter period. It has often been found that, in mammals, the early environment affects the development of the behaviour of an animal. In our study, however, we did not find abnormalities in cubs’ behaviour during the litter period. As it should be, the most frequent type of behaviour was play. Aggression was low, it did not rise in time and did not differ between the litters. We developed tests to identify personality types in European mink. We found that it is possible to distinguish individual mink in boldness, sociability and exploration. In summary, we found that the main reason why breeding fails in the European mink is in the behaviour of captive born males. The causes of behavioural distortion may not be related to the litter period, an analysis of personality types may help here. The knowledge obtained forms important basis information for the work aimed at improving keeping condition of captive European mink.
European mink is a critically endangered carnivore which has almost disappeared from nature. To save the species from extinction a captive population was established. Unfortunately, keeping wild animals in captivity always causes problems, just because in a zoo everything is different from the species’ natural habitat. In the case of the European mink, there are problems with breeding in captive conditions. Some animals will fail to produce offspring which may threaten the persistence of the captive population. In this doctorial thesis, I addressed the reasons of breeding failures and how to find solutions to this problem. At first we studied what affects the size and survival of the litter. We found that the weight and age of the mother are most significant. Additionally we studied the hormonal cycle of the females during the mating season and gestation. Results were expectable: the hormonal cycle followed a profile typical of the species. Analysing the diaries kept at Tallinn zoo for 20 years, we did not find that something is wrong on the females’ side. Instead, we found that the breeding problems are caused by males which have been born in captivity. Some males are aggressive toward the female during the mating attempt or remain passive. To understand the reasons for kind of behaviour, we focused on the childhood of the mink: we studied the interactions between the cubs during the litter period. It has often been found that, in mammals, the early environment affects the development of the behaviour of an animal. In our study, however, we did not find abnormalities in cubs’ behaviour during the litter period. As it should be, the most frequent type of behaviour was play. Aggression was low, it did not rise in time and did not differ between the litters. We developed tests to identify personality types in European mink. We found that it is possible to distinguish individual mink in boldness, sociability and exploration. In summary, we found that the main reason why breeding fails in the European mink is in the behaviour of captive born males. The causes of behavioural distortion may not be related to the litter period, an analysis of personality types may help here. The knowledge obtained forms important basis information for the work aimed at improving keeping condition of captive European mink.
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Keywords
euroopa naarits, ohustatud liigid, loomade käitumine, paljunemisedukus, tehiskeskkond, European mink, endangered species, animal behavior, reproductive success, artificial environment