BlogI was again recently thinking about aposematic warning colouration and how we see familiar animals and birds in the countryside and naturally view them through our own eyes, rather than how a wild animal or bird might see them, which of course could well be quite different in terms of the meaning and interpretation of that message purveyed (Howse, 2014, 2022). A good example is the peacock butterfly, Inachis io (Fig. 1a).
To us, when we see it on a buddleia flower probing and sucking up nectar via its unrolled proboscis, we generally think “Ah, what a beautiful butterfly with its rich red, blue and yellow colouring and eye spots on each of its four wings.” But the wings, both upper side and underside, are to some large degree coloured the way they are for a purpose: the dark underside (Fig. 1b) acts as cryptic camouflage when the butterfly is hibernating through the winter months in hollow trees, woodsheds, etc., the upper side as a startle pattern to shock or perhaps also warn a would-be predator, bird or mouse that it is potentially dangerous or noxious in some way (Oloffson et al., 2013; Howse, 2014).
These butterflies also emit hissing sounds and loud ultrasound clicks made via their wings being flicked when disturbed during their rest, which is also thought to discourage would-be attackers (cf. Oloffson et al., 2012 for more details). Since the insect, being cold-blooded, cannot readily fly off when disturbed during the winter, such sounds made by abrasion of the wing surfaces, are enough of a deterrent. Ditto flashing its wings suddenly to reveal its eye spots, appearing like a predator in its own right. During warmer times of the year, when the insect is out and about and active, such flash displays, perhaps lasting only a few seconds, may be enough to momentarily distract a would-be attacker, giving the butterfly time to escape. So rather than just being surfaces with no particular role in the life of the animal, they are in fact acting as advertising ‘bill boards’ in terms of its defence (Cott, 1940). In addition to these behaviours, years ago I showed that when Peacock butterflies, Small Tortoiseshells, Aglais urticae and Brimstones, Gonepteryx rhamni, all hibernating species, are captured and held between thumb and index finger when feeding on flowers (in this case lavender), such as would occur if held in the beak of a predatory bird, the insects remained perfectly still, feigning death, a behaviour not seen in other, non-hibernating species tested (Loxdale, 2017).
Other familiar creatures in our garden also have colouration that we may not at first grasp the significance of. We are all aware that many venomous or noxious animals very often display bright warning colouration, a bit like police cars do: vivid reds, oranges, yellow and blacks, in different arrangements to maximise the visual impact to would-be assailants. Usually these are ‘honest’ signals, i.e. the said animal displaying them really is dangerous in possessing venom (e.g. Eastern Coral snake, Micrurus fulvius) or its flesh is noxious to the taste if bitten into or consumed, being laced with toxic antifeedant chemicals, e.g., cardiac glycosides in the case of the Monarch butterfly, Danaus plexippus. Other animals use such colours in a ‘dishonest’ way, mimicking a venomous or noxious animal, e.g. harmless black and yellow patterned hoverflies (Syrphids) pretending to be wasps or hornets. Such signals can be so-called Batesian mimics, in which a particular animal mimics a definite venomous or noxious model, perhaps a closely related species e.g. some species of Passion flower (Helioconid) butterflies living in the American tropics. Or they may be Müllerian mimics ‒ that is an animal mimicking a broad group of aposematically-coloured animals. Thus, if the mimic sports a – say – black and yellow livery, as many hoverflies do, this is broadly mimicking wasps and hornets in general and even if the deception is not perfect, i.e. the mimic does not resemble the model that exactly, either in terms of morphologically or livery, the ruse may well be good enough to deter attack from a predator, or give it (the potential prey) time to make its escape (Cott, 1940; Howse, 2022).
Now returning to the theme of common animals that may show aposematic warning colouration, birds should surely be considered in this light. One that springs to my mind is the Eurasian Magpie, Pica pica (Fig. 2), a common bird, member of the crow family (Corvidae), predator and scavenger in gardens and especially these days, along roadways where they scavenge road kills (Loxdale, 2023).
As predators, they rob the nests of small birds of their eggs and presumably eat any small animals that come their way and turn out to be suitable prey. Now whether their flesh or feathers is/are actually noxious or not, I notice looking at videos on You Tube, that even domestic cats and wild foxes coming into suburban gardens are very wary of attacking them and that these birds seemingly harass the animals and try to scare them away from their (as they consider it) territory.
https://www.youtube.com/watch?v=YsJiLwzGh4g; https://www.youtube.com/watch?v=USN8spjKFlU
Is the striking black-blue and white livery of these birds truly aposematic? Of course without chemical testing, one cannot definitively say. On the other hand, other animals with such striking black and white livery are venomous or noxious in some way or other, including the European adder, Vipera berus (Fig. 3), North American skunks, e.g. striped skunk, Mephitis mephitis (Fig. 4), and the Sea Bunny, Jorunna parva (Fig. 5), a marine dorid nudibranch occurring in the seas off Japan, Tanzania, Papua New Guinea, Seychelles and Réunion (Wikipedia). Clearly, this colouration has been evolved to scare off would-be attackers, whatever they be.
As a final thought aboth mammal aposematism, the Giant Panda bear, Ailuropoda melanoleuca (Fig. 6) (now designated as a true member of the bear family and not a racoon), has as well known a very distinct black and white livery (Wikipedia). The Pandas are very feisty as adults, despite their cute and cuddly appearance, as I have witnessed on TV films about their mating behaviour, which is not ‘a bowl of roses’ by any stretch of the imagination. Rather, it is a fist/ jaw/claw fight in all but name.
Naturally, adult Panda bears are unlikely to be attacked by many/any predatory animals, if they know what is good for them. But the cubs are more vulnerable. The adults eat a diet largely comprising bamboo shoots. Bamboo is toxic, containing cyanogenic glycosides named taxiphyllin (Pensiriwan et al., 2011), which they can largely metabolise of less toxic compounds (~ 80%) (Huang et al., 2016). [The cuddly Koala bear, Phascolarctos cinereus, which is in fact a marsupial (family Phascolarctidae), not a true bear, also primarily eat a toxic plant diet, here Eucalyptus leaves, and can detoxify the toxic compounds therein using Cytochrome P460 enzymes; Johnson et al., 2018].
So, because weaned, sub adult Giant Panda are vulnerable to the predators that roam the forest in central China where they live, including the Asian black bear, snow leopard, jackal and yellow-throated marten (see www.panda.org and Wikipedia entry), the fact that the animals eat and absorb highly toxic cyanogenic glycosides may perhaps act as a deterrent for these creatures against such potential mammalian predators, hence the black and white warning livery. Surely, such coloration has evolved for some reason or other, and anti-predation defence seems to me as good as any.
Hugh Loxdale
References
Web articles
Giant panda: https://en.wikipedia.org/wiki/Giant_panda
Giant Panda predators: https://wwf.panda.org/discover/knowledge_hub/endangered_species/giant_panda/panda/kung_fu_panda_enemies_defences/
Sea Bunny: https://en.wikipedia.org/wiki/Jorunna_parva
Books and Scientific Journals
Cott, H. B. (1940). Adaptive Coloration in Animals (1966 reprint), London: Methuen and Co. Ltd, pp. 508.
Howse, P.E. (2014). Seeing Butterflies: Colour Patterns and Mimicry. Winterbourne, Berkshire: Papadakis, pp 176.
Howse, P. E. (2022). The Spider-Winged Cupid and the Platypus. Published by Butterflies and Amazonia, ISBN 978-1-7398856-3-2, pp.171.
Huang, H. et al. (2016). Dietary resources shape the adaptive changes of cyanide detoxification function in giant panda (Ailuropoda melanoleuca). Scientific Reports 6, 34700. doi: 10.1038/srep34700.
Johnson, R. N. et al. (2018). Adaptation and conservation insights from the koala genome. Nature Genetics, 50 (8), 1102–1111. doi:10.1038/s41588-018-0153-5
Loxdale, H.D. (2017). Butterflies playing ‘possum’: An adaptive behaviour related to winter survival? Antenna 41 (1), 11-16. Available online at: www.researchgate.net/profile/Hugh-Loxdale/research
Loxdale, H.D. (2023). Perspective: Are some brightly coloured European birds toxic? Frontiers in Ecology & Evolution. Published online 5 May, 2023. doi.10.3389/fevo.2023.1150576
Olofsson, M., Jakobsson, S. & Wiklund, C. (2012). Auditory defence in the peacock butterfly (Inachis io) against mice (Apodemus flavicollis and A. sylvaticus). Behavioral Ecology and Sociobiology, 66, pp.209-215. doi 10.1007/s00265-011-1268-1
Olofsson, M., Løvlie, H., Tibblin, J., Jakobsson, S. & Wiklund, C. (2013). Eyespot display in the peacock butterfly triggers antipredator behaviors in naïve adult fowl, Behavioral Ecology 24 (1), 305–310. doi.org/10.1093/beheco/ars167
Pensiriwan, S., Guharat, S. & Wananukul, W. (2011). A mass cyanide poisoning from pickling bamboo shoots, Clinical Toxicology, 49 (9), 834-839. doi: 10.3109/15563650.2011.618456
Photos (©):
Common adder, www.woodlandtrust.org.uk/trees-woods-and-wildlife/animals/reptiles-and-amphibians/adder/
Eurasian magpie, Barbara Cooper, www.naturespot.org/species/magpie
Giant Panda, J. Patrick Fischer, Creative Commons Attribution-Share Alike 3.0 Unported license.
Peacock Butterfly, upper side by Matt Berry; underside by Charles J. Sharp, Otmoor, Oxfordshire, Creative Commons Attribution-ShareAlike license (CC-BY-SA).
Sea Bunny, ww.reddit.com/r/aww/comments/46djus/sea_bunnies_are_latest_craze_in_japan_for/
Striped Skunk about to spray, Wallace Keck – City of Rocks National Reserve, Creative Commons Attribution-ShareAlike 4.0 license and the GNU Free Documentation License