Movement of pond-breeding amphibians in fragmented landscapes : responses of great crested newt (Triturus cristatus) to road mitigation
Environmental sciences; Biological sciences
Thesis or dissertation
- © 2017 Cátia Matos. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder.
With the increase of transportation system in the world, roads facilitate opportunities for human social and economic development. Roads are also the primary cause of multiple and diverse negative ecological effects. Habitat and wildlife populations are directly disturbed as roads contribute to habitat loss, habitat fragmentation and reduction of the quality of surrounding habitats. Barrier effects and traffic mortality are amongst the principal factors impacting species that need to move among important habitats to complete their life cycle leading to fragmentation, isolation and local population extinctions. Pond-breeding amphibians can be particularly impacted in this way, with mortality rates of 60-90% imposed by roads in some circumstances. Road mitigation measures, such as tunnels and associated fences, are implemented to manage this problem and restore connectivity at the landscape level in order to sustain migration and dispersal movements for amphibians and maintain metapopulation dynamics over the long-term.
In the UK, the demand for the implementation of these mitigation infrastructures has increased in the past decade as urban development reached a detrimental point for the European Protected Species, Triturus cristatus, the Great Crested Newt. Road mitigation measures for newt species are notoriously difficult to implement efficiently due to the behavioural characteristics of this group and the poor understanding of how it influences road mitigation effectiveness. Their ability to climb vertical surfaces, the poor capacity for crossing large distances over land and general avoidance of small, narrow structures such as tunnels are some examples of responses that may influence how planning and design of mitigation can support and facilitate patterns of movements for the species. There is no clear understanding of how these responses and patterns influence successful crossings and dispersal in the long-term in the UK or the rest of Europe. Therefore, it is challenging to predict mitigation long term effectiveness, provide evidence-based guidance to developers despite their substantial costs and potentially crucial importance for maintaining connectivity and dispersal for this European protected species.
The main aim of this study was to evaluate T. cristatus movement patterns in areas impacted by roads and at which road mitigation measures had been deployed in order to develop evidence-based improvements for the strategic planning and design of dispersal corridors for future mitigation. From a pitfall data monitoring scheme, I investigated the species’ behavioural traits at a road mitigation site to understand spatial and temporal patterns of movement. Also, I calculated regional connectivity indexes in a sub-urban area to understand the importance of spatial scale for movement when collecting species presence and absence data from local ponds. I measured short-term behavioural responses to a road mitigation system during two diferent seasons using non-invasive marking techiniques. And finally, I relate how local climatic factors affect successful crossings in tunnels and overall use of a mitigation system using standard monitoring data from previous chapter pitfall data. These results showed seasonality and yearly movements having an important role in calculating successful use of mitigation and directionality of movement. Newts’ movements were higher in the course of autumn dispersal than at other times of year, and movement between patches varied greatly among years. Fences operated as a barrier to dispersing newts, potentially preventing road mortality but also reducing dispersal. Landscape analysis showed how annual home-range position and size affects connectivity at regional level for newts when considering roads as barriers. Predicted dispersal patches increased with landscape permeability, which was associated with road type; minor roads were more permeable. Behaviour analysis towards responses in a road mitigation system showed distance of short-term movements changing significantly around the fences. These responses were independent of newts’ age. And finally, local weather patterns influenced newts’ successful crossings among years.
These results showed the multi-scalar perspective of responses of T. cristatus to road mitigation systems and indicate the need to include consideration of multiple spatial and temporal scales when predicting the consequences of road construction and mitigation on T. cristatus metapopulation dynamics and hence conservation status. Identification of patterns of responses according to individual circumstance (age, sex) and climatic conditions facilitated calculation of potential landscape connectivity at distinctive spatial and temporal scales, and could inform improved advice for system design. Clear definitions of mitigation effectiveness have been repeatedly called for, but rarely offered. Here we have shown how spatial and temporal scales of newt responses need to be incorporated into these definitions, but also how variable they can be. Consequently, during and following road mitigation we recommend that newt responses should be monitored at these multiple scales to inform an adaptive approach to T. cristatus conservation when they are threatened by roads. The ultimate goal would be to include response patterns, scales and variability in a new iterative and innovative management tool that enables estimation of mitigation effectiveness for T. cristatus landscape connectivity over the short- to long-term.
- School of Environmental Sciences, The University of Hull
- Petrovan, Silviu O.; Ward, Alastair (Alastair Iain); Wheeler, Philip M.
- Sponsor (Organisation)
- University of Hull; Natural England (Agency)
- Qualification level
- Qualification name
- 7 MB