How to Care for Hibernating Butterflies

In Ireland, we have four butterfly species that over-winter in the adult form.  We have a number of moths that hibernate as adults. One of these is the iconic Herald moth. A group of this species will sometimes shelter in your attic to wait for spring.

One of our butterflies has a habit of entering rooms in houses to pass the winter. The Small Tortoiseshell, a beautifully marked butterfly likes to stay close to us in late summer and will even stake out likely hibernation sites indoors especially during August and September before settling to fold its wings for winter in some obscure spot in our homes, sheds or even cars! This well-studied butterfly has some fascinating characteristics. It has shown an ability to relocate specific sites when it has been disturbed from the site, suggesting a spatial memory; if a nettle on which a female is laying her eggs is moved, the female returns to the spot where the nettle was located, not to the site it was removed to. The butterfly is very mobile and some of ‘our’ Small Tortoiseshells may have travelled from Britain and Europe. Males establish and defend territories but if he finds a female he switches to defending the female from other males. She makes him work hard by flying away at speed to see if he can keep up and sometimes by flying into territory held by other males so that her suitor may have to fight several males throughout the rest of the day. He will drive them away by engaging in a series of aerial combats, with high altitude climbs when he tries to fly above the intruder. When the intruder is expelled, the male returns to his female who usually remains perched where he left her. Sometimes, though, she gives him the slip, giving him an anxious search as he inspects the surrounding nettle bed for her. Some females hide, and later accept defence by another male. Even a female who has cooperated with a male all day tries to lose him when she goes to roost in the nettles in the evening by dropping into the nettles and running along the ground. If the male manages to stay with her, she suddenly becomes quiet and allows mating, which lasts all night. Presumably, her demanding behaviour ensures that only the fittest males father offspring, ensuring the health of the next generation. This provides a fascinating example of selection by the female of the fittest male.

Another, related feature of the butterfly is its impressive longevity. The over-wintering generation is long-lived, and individuals can survive 10 months. The impressive life-span allows the female Small Tortoiseshell the chance to be selective; most female butterflies accept the first male encountered; these females lack the luxury of an extended life to test male powers of endurance.

However, our Small Tortoiseshells have one significant challenge when they enter our homes to see out the winter in our bedrooms, living rooms and hallways. The butterflies are very careful to select the best spots, picking excellent hiding places in curtain folds, behind mirrors and pictures, in unused chimney brests, behind dressers and, to complete the concealment, their dark cryptic coloured undersides blend nicely with their chosen surface. However, the mod con that is central heating confounds their attempts to complete their winter slumber. Heat rouses the butterfly, causing it to believe that spring, with its sunshine, flowers and nettles beckon it to fly outdoors. The confused butterfly flies around lights and windows, trying to get out.

Householders who release the butterfly into the winter are usually dooming it. The butterfly rapidly loses the ability to fly when its body temperature plummets in the cold and is picked off by birds or mammals. The other problem is starvation. The butterfly built up vital fats by gorging on nectar in our gardens and countryside before switching off for winter and long periods of unseasonable activity reduces these reserves.

What should you do if you encounter an active Small Tortoiseshell in your home?

If this happens in warm spring weather release the butterfly in the knowledge that it’s time to let it go. It is now ready to feed on the spring flowers, move in search of territories, breeding grounds and mates.

If the butterfly wakes up in winter it should be placed in a dry, transparent container lined with a folded section of kitchen roll to absorb moisture and placed in the salad drawer in the fridge, where the temperature is around four Celsius. The butterfly will soon settle and can be kept there until warm, sunny weather arrives in March or April.  Alternatively, remove the butterfly from the container when it is quiet and place in an unheated shed or room to complete its winter rest.

If the butterfly has been flying around for some time, it may need to be fed. Dissolve sugar or honey in hot water, allow it to cool and use a cotton pad to absorb the sweetened solution. When cool, place the calmed butterfly (cooled in the salad drawer but not long enough to be made fully docile) on the pad, in softly-lit mild conditions. It should begin to feed. When it has finished, place in a cool place to sleep.

Over the years I have successfully over-wintered adult Small Tortoiseshells and felt a burst of delight to watch the butterfly surge into the sunshine in spring. Interestingly, the released butterfly does not loiter. It flies strongly away, as though hyper-energised by the promise of brightness and freshness of a world renewed by the return of sunshine.

Small Tortoiseshell.©J.Harding.

Happy Christmas

Butterfly Conservation Ireland wishes our members, supporters, friends and your families a  joyful and peaceful Christmas season.

Thank you for your enthusiasm and support during 2017.

Here is a photograph of a beautiful Peacock butterfly, taken on our reserve at Lullybeg, County Kildare on Wednesday 23rd of August, 2017. This lovely butterfly is now tucked up for the winter.

We look forward to seeing this butterfly and many others in the new year!



Winter Cold a benefit for Butterflies

It is December 8th and the Met Office is forecasting a bitterly cold month ahead. How will this impact on our butterflies? Butterflies are regarded as creatures of the light, lovers of sunshine and warmth, vulnerable to the onslaught of bitter winters.  We rarely have cold winters and with climate warming we may get even fewer, so how will this change the fortunes of our butterfly and moth populations? The connection between extreme winter warmth and butterfly population levels was researched by East Anglia University, Butterfly Conservation UK and  the Centre for Ecology and Hydrology (McDermott Long, O., Warren, R., Price, J., Brereton, T. M., Botham, M. S. and Franco, A. M. A. (2017), Sensitivity of UK butterflies to local climatic extremes: which life stages are most at risk?. J Anim Ecol, 86: 108–116. doi:10.1111/1365-2656.12594).

It was already known that butterflies do better in warmer summers but, perhaps unexpectedly, the new research which looked at the impact of extreme climate events on the population of butterflies in the UK from 1976-2012 revealed that extreme mild winters have a negative effect on the populations of just over half of the 41 species studied.  It is interesting to observe that these negative effects occurred regardless of whether the species affected are widespread  species or habitat specialists.  All four of our butterflies that over-winter in the adult form, the Comma, Small Tortoiseshell, Peacock and Brimstone showed a negative impact of extreme winter warmth (disruption of over-wintering in these species may result in losses from predation and decline in fat reserves). Species that showed a similar result and the stage in which these over-winter are the Purple Hairstreak (egg), Dingy Skipper and Dark Green Fritillary (larva) and Orange-tip (pupa).

Only two of the species studied showed that there is a positive effect of warm winters; these were Wall Brown and Holly Blue. Extremely cold winter days were associated with significant population increases in the Large White (over-winters as a pupa) and Ringlet (over-winters as a larva).

Overall, the study found that cold spells in winter were beneficial or neutral in the impacts on population size while warm spells in winter were generally harmful. An additional and unexpected finding is that the pupa of butterflies that have one brood per year show sensitivity to extreme precipitation.

Another recent study, from Stockholm University  also using data from the UK (Stålhandske, S., Gotthard, K. and Leimar, O. (2017), Winter chilling speeds spring development of temperate butterflies. J Anim Ecol, 86: 718–729. doi:10.1111/1365-2656.12673) found that some butterflies that over-winter in the pupal state emerge earlier in the year during a warm spring but not after a warm winter. Three species of the five species studied, Green-veined White, Orange-tip and Green Hairstreak flew earlier in spring after a cold winter. The study found that warm winters delay emergence. This earlier spring emergence might be due to the insect being programmed to emerge from the pupa after experiencing a prolonged period of cold followed by a period of warm conditions; this temperature change process is used to obtain  specimens out of season in captivity. This involves placing a pupa in a refrigerator for some weeks and then keeping it at room temperature which causes early emergence,  mimicking the effects of the passing of winter and onset of spring.

With climate change expected to continue, what  are the main implications for our species? The findings are mixed. Warmer summer weather, as long as drought does not occur, may well help populations to increase and spread. Extreme climate events, such as extreme warmth and extreme rainfall in winter may cause declines. High quality habitats may have the ability to buffer extremes, so it is vital that habitats are managed as carefully as possible to provide the best chance of survival for our butterflies and moths.

When you see the snow and ice over the coming days, please take care, but remember that our butterflies are well-adapted to these conditions which may be necessary for their long-term survival. Snow and butterflies are compatible!

Well managed, landscape-scale habitats may be vital to protect butterflies and moths from climate change.© J.Harding.
The Orange-tip flies earlier in spring after a cold winter but suffers from extreme winter warmth. © J.Harding.