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ABSTRACT - Tadpoles with a trick: Overwintering Ecology of tadpoles in a Himalayan stream
Abstract
Abstract of the conference oral presentation which won the 'Best Oral Presentation Award' instituted by the Student Naturalists Association, Jagiellonian University.
Keywords: amphibian, metamorphosis, cold, development, life-history strategy, plasticity, modification
... The other species is the Himalaya paa frog Nanorana vicina (Dubois, 1976) that is distributed in the Himalayan front of India, north-central Pakistan from Kashmir, Himachal Pradesh to Punjab, and Uttarakhand ranging from 2000-3000 m a.s.l. and is associated with montane streams, springs, fountains and other running water within open forest and grassland habitats Frost 2021). Apart from morphological descriptions and other natural history records, little is known of the larval ecology of either species (Das & Dutta, 2007;Sircar, 2010;Banerjee et al., 2020;Gill et al., 2020;Jithin, 2021). Jithin (2021) reported overwintering tadpoles of N. minica and N. vicina from the western Himalaya, India. ...
... Jithin (2021) reported overwintering tadpoles of N. minica and N. vicina from the western Himalaya, India. The overwintering tadpoles feed on periphyton growing on check dam walls, bedrocks, boulders, cobbles, leaf litter surface, submerged logs in the pool; humus and animal carcasses; the check dam pools also offer a temperature gradient (Boix-Fayos et al., 2007: Banerjee et al., 2020Jithin, 2021 Annual maintenance of check dams is essential. Water is usually diverted from the original channel making the area dry apart from a few shallow pools that act as refugia for aquatic organisms. ...
... The size of these tadpoles ranged from 25.32 to 63.4 mm (total length) and stages from 26 to 36 (Gosner, 1960). We could not quantify the deaths of two species separately as field identification is difficult (Jithin, 2021). Apart from the mortality of tadpoles, newly laid egg strings of Himalayan toad Duttaphrynus himalayanus were also found in the dried stream bed. ...
We report the deaths of overwintering tadpoles of Nanorana spp. during check dam maintenance events causing localised droughts along the Dhobhighat (Ringali Gad) stream, flowing through the Mussoorie Wildlife Sanctuary, Uttarakhand, India; and discusses the conservation issues and further research required in the scenario.
... Neotropics, Oriental and Sino-Japanese regions lack research and documentation of overwintering in anuran larvae in general, and there are no studies from the Indian region (Jithin, 2021). The lack of studies on tadpole behavioural ecology in the country considering the species richness, endemism, climatic variability and habitat heterogeneity has been reported previously (Saidapur, 2001;Sircar, 2010). ...
... The lack of studies on tadpole behavioural ecology in the country considering the species richness, endemism, climatic variability and habitat heterogeneity has been reported previously (Saidapur, 2001;Sircar, 2010). Jithin (2021) documented overwintering tadpole populations of Nanorana sp. in the state of Uttarakhand; Mussoorie, Dhanaulti and Devalsari. The present study investigated the behavioural aspect of the larval overwintering ecology, as it is a survival strategy of the Himalayan stream breeding frogs that remains poorly understood, and is the first of its kind from India. ...
... The overwintering tadpoles present in the study site belong to Nanorana vicina and N. minica (Dicroglossidae) (Banerjee et al., 2020;Jithin, 2021). N. minica (Small Paa Frog or Nepal Paa Frog) is listed as a vulnerable species in the IUCN Red List (Ohler et al., 2004) with poorly known larval ecology and larval descriptions of varying levels of completeness (Das and Dutta, 2007). ...
Delaying metamorphosis in low-temperature conditions by anuran larvae known as ‘overwintering’ have been poorly studied, especially in terms of habitat ecology and behavioural aspects. The present study investigates some of the ecological aspects of overwintering tadpoles of the genus Nanorana in the Western Himalaya in an anthropogenically modified stream where check dams have altered the natural habitat, which can potentially influence the amphibian ecology. We present insights on the influence of check dams on the tadpole activity pattern and morphometric traits useful in the conservation planning of the narrowly distributed and understudied species, which are most sensitive to habitat modification.
We monitored natural and modified pool habitats in the stream during winter and post-winter seasons based on the visual density of tadpoles to assess the diurnal and seasonal emergence pattern with associated habitat variables. Generalized Linear Mixed Modeling (GLMM) was used to understand the influence of various habitat variables on the visible density of tadpoles. Fine-scale temporal scan sampling of tadpoles was carried out to complement the understanding of the visible density variation and analyzed using circular plots and activity overlap estimation. Variation in morphometric traits was assessed using field morphometry and photogrammetry.
Mean tadpole visible density at nighttime was higher in modified pools than natural pools during winter, but there was no statistically significant difference during daytime; the nocturnal pattern changed in the post-winter, where visible density was higher in natural pools. Tadpole visible density was influenced by the interaction of mean canopy cover with water temperature, instream cover items richness, mean canopy cover percentage, water temperature, leaf litter depth, water velocity and interaction of time of the day with pool modification. Tadpole activity patterns varied significantly between pool types during post-winter, where modified pool population increased daytime activity and thus the activity overlap reduced from winter (90.8%) to post-winter (64.5%). During both seasons, the mean body size of the natural pool population was significantly lower than the modified pool population; mean relative tail length was significantly lower in natural pools during post-winter; mean tail depth was significantly lower in natural pools during winter.
The study presents evidence of the influence of anthropogenic habitat alterations on behaviour and morphometric traits of overwintering tadpoles, which needs to be further investigated. We also discuss the variation in nocturnal emergence, habitat selection and morphometric trait patterns in the modified habitat, potential reasons and similar behaviour in other aquatic organisms, which need to be considered while developing conservation strategies for the overwintering tadpoles in the region.
Data Availability Statement
All relevant datasets used in this study are available through Zenodo (Jithin et al., 2022; DOI: 10.5281/zenodo.6327687).
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