Editorial Type:
Article Category: Other
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Online Publication Date: 01 Mar 2014

Assessing Historical and Current Threats to Common Frog (Rana temporaria) Populations in Ireland

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Page Range: 13 – 19
DOI: 10.1670/12-053
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Abstract

Ponds are an ephemeral feature of the landscape but their large-scale loss can have profound implications for biodiversity and the persistence of amphibian populations. We quantified rates of pond loss throughout Ireland over a period of approximately 125 yr. Environmental parameters and perceived risk factors associated with the current occurrence and density of the Common Frog, Rana temporaria, were also analyzed. The numbers of farmland ponds declined by 54% between 1887–1913 and 2005–11, with most ponds and the greatest losses in the East, coincident with agricultural intensification and human habitation. The decline of pond numbers was significant but, at approximately 0.5% per annum, was substantially less than losses recorded in other European countries. Losses were coincident with major changes to the agricultural landscape including extensive land drainage. However, losses of pond and natural wetland habitats throughout Ireland may have been partially or wholly mitigated by a synchronous expansion of artificial field margin ditches associated with drainage projects during the mid-20th Century. The ecology of the Common Frog in Ireland was similar to its ecology elsewhere and it appears largely unaffected by pollution and disturbance. Consequently, the conservation status of the frog in Ireland was judged “favorable” and should remain so for the foreseeable future.

Copyright: 2014
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. 1. 
F ig . 1. 

A 1-km Irish grid square (T1030, Co. Wexford) showing (a) five extant ponds (red polygons) between 1887–1913 of which (b) four remained extant during 2005 and (c) where confirmed during 2011 using a ground-truthed survey. Thus, absolute net change for this square was −1 pond (circled in blue) and relative net change was −20% of original ponds.


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F ig . 2. 

(a) Pond loss in terms of absolute net change throughout Ireland between 1887–1913 and 2005–11 and (b) the current number of extant ponds during 2005–11.


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Fig. 3 . 

Mean (A) site occupancy and (B) frog density at various water body types ± 95% confidence intervals. Sample sizes (N) are given in parentheses on the x-axis labels. Minor categories, including lakes or reservoirs (N = 7), turloughs (N = 2), and other types (N = 1) were excluded. The effect of the presence of (C) fish and (D) waterfowl on mean frog density ± 95% confidence intervals.


Contributor Notes

Corresponding Author. E-mail: neil.reid@qub.ac.uk
Accepted: 04 Oct 2012
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