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Groddjur på Gotland 2002
2003 (Swedish)Report (Other academic)
Abstract [sv]

Gotlands tre groddjur - åkergroda (Rana arvalis), vanlig padda (Bufo bufo) och mindre vattensalamander (Triturus vulgaris) - inventerades våren 2002 i tio 5 x 5 km rutor jämnt fördelade över Gotland. Totalt besöktes 324 objekt inom dessa rutor vid två eller tre tillfällen, under och precis efter leken. Förekomst eller icke förekomst av samtliga arter noterades. Vid de objekt där groddjur påträffades uppskattades dess-utom den lokala populationsstorleken för respektive art. Hos åkergrodan räknades antalet romklumpar (detsamma som antalet honor), för vanlig padda och mindre vattensalamander användes ett relativt index baserat på det uppskattade antalet rom-strängar (vanlig padda) respektive observerade adulter (mindre vattensalamander). Alla tre arterna var väl spridda över Gotland: mindre vattensalamander hittades i alla tio rutorna, åkergroda i nio och vanlig padda i åtta av de tio rutorna. Åkergroda fanns i 27% av alla objekt, vanlig padda och mindre vattensalamander i 27% respektive 32% av alla besökta objekt. Alla arter var relativt ovanliga i de områden där andelen åkermark var hög. Det genomsnittliga antalet romläggande åkergrodshonor per inventerat objekt var bara 54 honor, vilket är lågt i jämförelse med jämförbart estimat för fastlandspopulationerna (169 honor). Detta indikerar att den genomsnittliga lokala populationsstorleken för gotländska åkergrodor är mycket mindre än på fastlandet. En alternativ förklaring är att populationsstrukturen skiljer sig mellan Gotland och fastlandet. Fyrtiofem objekt vilka hade förekomst av minst 20 åkergrodshonor och som är lättinventerade valdes ut så att ett övervakningsprogram av Gotlands groddjur kan sättas upp.

Abstract [en]

The occurrence and abundance of the three Gotlandic amphibian species (moor frog, Rana arvalis; the common toad, Bufo bufo; the smooth newt, Triturus vulgaris) was determined in spring 2002 in ten 5 ´ 5 km squares. A total of 324 individual objects within these squares were visited 2-3 times during and after the spawning period, and the presence or absence of all species was noted. In addition, all moor frog-spawn clumps were counted to estimate local female population sizes. For the common toad and smooth newt a relative population size index was devised on the basis of spawn strings and the occurrence of adults, respectively. The results show that all species have a wide distribution on Gotland: the smooth newt was encountered in all, the moor frog and the toad in nine and eight of the ten 5 ´ 5 km squares censued, respectively. Moor frogs were encountered in 27% of the censued localities, whereas common toads and smooth newts were encountered in 27 and 32% of the localities, respectively. All species were relatively scarce in areas where the proportion of agricultural landscape was high. The average number breeding R. arvalis females per locality were 54 females, which is a relatively small figure as compared to the situation on the mainland (169 females per locality). In general, the relative abundances of the three different species were correlated across the localities, suggesting that similar types of localities are favoured as breeding sites by all three species. A subset of 45 easily censuable localities having a moor frog female population size of at least 20 individuals were selected to form a suitable set-up for further monitoring purposes of population trends of Gotlandic amphibians.

Place, publisher, year, edition, pages
Visby: Länsstyrelsen , 2003. , 59 p.
Series
Rapporter om natur och miljö, ISSN 1653-7041 ; 2003:3
Keyword [sv]
groddjur, Gotland, åkergroda, Rana arvalis, vanlig padda, bufo bufo, mindre vattensalamander, Triturus vulgaris
National Category
Environmental Sciences
Research subject
Environmental Objectives, A Rich Diversity of Plant and Animal Life; Environmental Objectives, Thriving Wetlands
Identifiers
URN: urn:nbn:se:naturvardsverket:diva-6389OAI: oai:DiVA.org:naturvardsverket-6389DiVA: diva2:908637
Available from: 2016-03-03 Created: 2016-03-03 Last updated: 2016-03-10Bibliographically approved

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Environmental Sciences

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