Small Tortoiseshell (Aglais urticae)
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© Nick Greatorex-Davies
The Small Tortoiseshell is a very mobile species that can be found almost anywhere and is a frequent sight in gardens and visitor to Buddleia bushes. Larvae feed gregariously on Stinging Nettle (Urtica dioica) in open sunny situations. (For further details on this species see http://www.butterfly-conservation.org/).
Status details :
Status since 1976 is Rapid decline with a decrease of -75.1%
Status over the last 20 years is Stable with a decrease of -39.7%
Status over the last 10 years is Stable with a increase of 84%
Log collated index plot
This chart shows the index of abundance (LCI = Log Collated Index) over time. It shows fluctuations in
populations from year to year, and is scaled so that the average index over the whole series is equal to 2
(horizontal line). For greater detail about how this index is derived, click on the green question mark above.
Trend description :
The data show a significant decline in the Small Tortoiseshell since 1976. Although this species does generally show annual fluctuations in abundance, the recent pattern of underlying decline has seen it regularly produce some of its lowest indices of the series. There were fears that an introduced parasite of Nymphalid butterflies, the Tachinid fly, Sturmia bella, which was first recorded in Britain in 1998, might be having an adverse effect on this butterfly. However numbers climbed steadily after that, and the 2003 index was one of the highest in the series. Although the parasite is now found all over southern Britain there is no evidence so far that the parasite is badly affecting any Nymphalid species and there are clearly other factors involved.
This map shows the distribution between 1995 and 2016. Data is derived from the Butterflies for the New Millenium dataset via the NBN Gateway
This chart shows the average number of butterflies seen on transects between Arpil and October across all sites (fitted values from a Generalised Additive Model). The blue line gives average counts over the full BMS series (1976 to date) and the red line gives the average for the last year.
This map shows symbols for the mean abundance at transect sites, with the colour of the symbol reflecting the level of abundance. Means are over all years. Grey background squares are the occupied cells as shown by the Butterflies for the New Millenium over the previous ten year period.
In total, Small Tortoiseshell has been recorded from 897 transects in the Butterfly Monitoring Scheme. Of these, annual indices of abundance have been calculated from 1035 sites, with an average index of 29 individuals per site.
For 469 of these sites, Small Tortoiseshell has been recorded well enough to calculate annual indices of abundance in more years, allowing trends to be calculated.
In 2017, 6636 individuals were recorded from 535 sites, producing annual indices at 386 of these.
Links to counts
This map shows the trend in abundance at particular transect sites for which data has been received within the last five years. Trends (increasing, declining or stable) are assessed at sites where the species has more than five years of annual index data. Use the option boxes below to view plots for individual sites.
Links to lists of sites with particular statuses
|Extinct sites (4)|
|Stable sites (645)|
|Increasing sites (24)|
|Declining sites (169)|