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Monitoring and Assessment of the Distribution of the Dice Snake in Ticino, Southern Switzerland


Mebert, K; Conelli, A E; Nembrini, M; Schmidt, B R (2011). Monitoring and Assessment of the Distribution of the Dice Snake in Ticino, Southern Switzerland. In: Mebert, K. The Dice Snake, Natrix tessellata: Biology, Distribution and Conservation of a Palaearctic Species. Rheinbach: Deutsche Gesellschaft für Herpetologie und Terrarienkunde, 117-130.

Abstract

Based on a two-year monitoring, we analysed the distribution of dice snake populations in the Canton of
Ticino (Switzerland). Imperfect detection was taken into account in order to avoid underestimation of the distrubtion
range and hence overestimating the species threat status: we therefore used a model based on a mark-recapturelike
approach to estimate detection probability, which was 61.2% (± 6.8%; standard error), and site occupancy, which
was 78.0% (± 7.9%). Detection probability depended on habitat characteristics (tree cover and naturalness of the
streams and lake shores) while occupancy was best predicted by the number of previous dice snake records at a site.
We observed local decline or extinction of some small populations located on secondary streams, apparently because
of habitat deterioration. However, populations located on lakes (Lugano, Maggiore) and main rivers (Ticino, Brenno,
Maggia, Vedeggio and Tresa) showed no signs of decline and rather high densities. Therefore, the status of Natrix tessellata in Ticino should be considered as stable. The endangered status reported by the Swiss Red List for these species is adequate because of the small area occupied at national level (IUCN criteria B2a, B2b (iii, iv)) and vulnerability of freshwater ecosystems. A specific action plan in favour of the conservation of dice snakes populations in Ticino, Switzerland, will now be based on the collected data.

Abstract

Based on a two-year monitoring, we analysed the distribution of dice snake populations in the Canton of
Ticino (Switzerland). Imperfect detection was taken into account in order to avoid underestimation of the distrubtion
range and hence overestimating the species threat status: we therefore used a model based on a mark-recapturelike
approach to estimate detection probability, which was 61.2% (± 6.8%; standard error), and site occupancy, which
was 78.0% (± 7.9%). Detection probability depended on habitat characteristics (tree cover and naturalness of the
streams and lake shores) while occupancy was best predicted by the number of previous dice snake records at a site.
We observed local decline or extinction of some small populations located on secondary streams, apparently because
of habitat deterioration. However, populations located on lakes (Lugano, Maggiore) and main rivers (Ticino, Brenno,
Maggia, Vedeggio and Tresa) showed no signs of decline and rather high densities. Therefore, the status of Natrix tessellata in Ticino should be considered as stable. The endangered status reported by the Swiss Red List for these species is adequate because of the small area occupied at national level (IUCN criteria B2a, B2b (iii, iv)) and vulnerability of freshwater ecosystems. A specific action plan in favour of the conservation of dice snakes populations in Ticino, Switzerland, will now be based on the collected data.

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Additional indexing

Item Type:Book Section, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Language:English
Date:2011
Deposited On:20 Jan 2012 17:01
Last Modified:22 Nov 2017 19:59
Publisher:Deutsche Gesellschaft für Herpetologie und Terrarienkunde
Series Name:Mertensiella
Number:18
ISSN:0934-6643
ISBN:978-3-9812565-4-3
Related URLs:http://www.ieu.uzh.ch/staff/leaders/benischmidt.html (Author)

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