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Grass snakes exploit anthropogenic heat sources to overcome distributional limits imposed by oviparity
Stockholm University, Faculty of Science, Department of Zoology.
Stockholm University, Faculty of Science, Department of Zoology.
2010 (English)In: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 24, no 5, 1095-1102 p.Article in journal (Refereed) Published
Abstract [en]

P>1. A lack of warm nest-sites prevents oviparous reptile species from reproducing in cool climates; such areas are dominated by viviparous species because sun-seeking pregnant females can maintain high temperatures for their developing offspring. 2. Our field and laboratory studies show that one oviparous species (the grass snake, Natrix natrix) escapes this cold-climate constraint (and hence, extends much further north in Europe than do other oviparous taxa) by ovipositing in a thermally distinctive man-made microhabitat (manure heaps on farms). 3. In the field, temperatures inside manure heaps averaged 30 center dot 7 degrees C, much higher than compost heaps (20 center dot 6 degrees C) or potential natural nest-sites under logs and rocks (15 center dot 5 degrees C). 4. In the laboratory, higher incubation temperatures not only hastened hatching, but also increased hatching success and modified the body sizes, colours, and locomotor abilities of hatchlings. Incubation temperatures typical of manure heaps (rather than alternative nest-sites) resulted in larger, faster offspring that hatched earlier in the season. 5. Thus, anthropogenic activities have generated potential nest-sites offering thermal regimes not naturally available in the region; and grass snakes have exploited that opportunity to escape the thermal limits that restrict geographic distributions of other oviparous reptile taxa.

Place, publisher, year, edition, pages
2010. Vol. 24, no 5, 1095-1102 p.
Keyword [en]
geographic distribution, maternal manipulation hypothesis, natricine, reproductive mode, thermoregulation, viviparity
National Category
Biological Sciences
Research subject
Animal Ecology
Identifiers
URN: urn:nbn:se:su:diva-50179DOI: 10.1111/j.1365-2435.2010.01730.xISI: 000281895800018OAI: oai:DiVA.org:su-50179DiVA: diva2:381916
Note

4

Available from: 2010-12-29 Created: 2010-12-21 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Nesting ecology of the grass snake (Natrix natrix) and its implications for conservation
Open this publication in new window or tab >>Nesting ecology of the grass snake (Natrix natrix) and its implications for conservation
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The onset of agriculture about 12,000 years ago has had a major influence on the biodiversity of plants and animals. Unfortunately, the rapid changes in agricultural practices that has occurred in recent times has negatively affected many farmland species. One such species is the grass snake (Natrix natrix), which has been reported to decline in many parts of Europe, including Sweden. The grass snake is unique, not only in that it is the most northerly distributed oviparous reptile in the world, but also because of its habit of using anthropogenic heat sources such as manure heaps and composts as nesting-sites. Unfortunately changes in manure management and abandonment of farmlands have resulted in a decline and fragmentation of these environments. This may pose a threat for the northernmost populations of the grass snake, because natural nests in these areas may not provide sufficient heat for the eggs to hatch. The eggs and embryos of reptiles are highly sensitive to incubation temperatures, which can influence not only hatching success but also many phenotypic traits in the hatchlings. In this thesis I used a series of laboratory and field experiments to investigate the importance of anthropogenic heat sources for the reproductive ecology of cold-climate populations of grass snakes.  More specifically, I aimed to investigate thermal regimes of nests and how they influence embryonic development and offspring traits associated with survival and fitness. The results showed that manure heaps and composts are significantly warmer than potential natural nests and that natural nests do not provide sufficient heat to sustain embryonic development. Further, manure heaps were warmer and more constant in temperature than composts, resulting in higher hatching success and earlier hatching in manure heaps. The higher thermal variability in composts increased the frequency of abnormalities that are likely to negatively affect survival and fitness. In conclusion, this thesis shows that the use of anthropogenic heat sources has enabled grass snakes to expand their range farther north than any other oviparous reptile and that the thermal dichotomy in the primary nesting environments used by grass snakes contribute to important life-history variation in this species. These findings have important implications for conservation of reptile populations in general and grass snakes in particular.  

Place, publisher, year, edition, pages
Stockholm: Department of Zoology, Stockholm University, 2016
Keyword
agriculture, anthropogenic, climate, embryonic development, incubation
National Category
Ecology
Research subject
Animal Ecology
Identifiers
urn:nbn:se:su:diva-125524 (URN)978-91-7649-307-6 (ISBN)
Public defence
2016-02-19, Vivi Täckholmsalen, Svante Arrhenius väg 20 A, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2016-01-27 Created: 2016-01-13 Last updated: 2017-02-23Bibliographically approved

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