biology zoology blog benno meyer rochow invasive traces

Telltale Signs in Snow, Mud and Sand

The tracks that animals left behind  

Winter is the season of concerts, ballet performances, rich food and winter sports, but you don’t need to be a skier to enjoy a walk in the snow. There’s a lot to see and even though I used to get cold when on a winter forest walk with my grandfather, he always found something exciting to show me in the snow (and at the end of the walk there always was the hot bouillon in the restaurant). The footprints in the snow (so aptly celebrated in a song by Bill Monroe) left by various animals can actually tell stories. “Here, a marten has chased a squirrel”, my grandfather would point out to me. A little further we’d notice footprints of a deer and then some wild pig. The fox’s prints and the rabbits are the easiest, I remember. And the tiny little ones with a thin line are from rats or mice with their long tails.

Footprints are not restricted to snow, but also visible in sand (Australian Aborigines and African Sān are the world’s best ‘readers’) unless the wind covers them or the rain washes them away. When I was in North Korea I saw a newly married couple write their vows with their fingers into the wet sand of the beach, only to see their semi-secret wishes get erased by the next wave. But there are, of course, beaches that have footprints that did not become erased, but became lithificated, which means they became fossil footprints. Originally made by heavy animals in wet sediments, e.g. mud, they hardened and became preserved and are now visible in various places on Earth. In Scotland the island of Skye is famous for its 165 million year old dinosaur footprints visible at low tide and on the beach near the town of Broome in Western Australia there must have been a real stampede of dinosaurs who left more than 1000 footprints on sandstone 130 million years ago when there was a river delta in that region. The largest ever seen footprint of 1.7 m in diameter probably belonged to a Brontosaurus. It is amazing to read that some ‘collectors’ even tried to dig out some of these prints, which is a highly illegal activity.

Footprints of animals that lived millions of years ago are found in all regions of the world, but apart from the sites mentioned above, those from Portugal, the Andes, Arizona and Sth. Korea are particularly well studied. Several criteria are used to match the footprints and the animals that made them. To determine the age and the type of the sediment is important; size and shape of the imprint are also important and number and lengths of the toes can be a “giveaway”. Web-footed tracks are known from South Korea and three-toed prints (the middle toe being the longest) are typical of the prints from the Scottish island of Skye. The prints not only tell the palaeontologist who has walked along a particular area how many million years ago, but they also provide information on the type of gait used by the animal and whether an individual was a member of a group, was chased by a predator or perhaps was an injured and limping individual. Fossil footprints are known from dinosaurs, birds, mammals, lizards, and even arthropods. Fossil prints from Sth. Korea have even shown that some crocodiles might have moved around on 2 legs.

Of course, all the footprints are the result of depressions in the substrate (one should think). But I observed something peculiar when in Antarctica: my footprints did not leave depressions in the snow, but turned into the opposite: positive, raised footprint reliefs! The reason was that the Polar snow was so fine and powdery that it was immediately blown away by the wind except for the area where the weight of my foot had compressed it. Raised footprints in the snow: a unique feature of Antarctica!

© Dr V.B. Meyer-Rochow and, 2020.
Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and with appropriate and specific direction to the original content. 

biology zoology blog benno meyer rochow invasive species

Wanted and Unwanted Immigrants

And I don’t mean humans

A few years ago the “killer bee invasion” was feared in the USA; now it’s the “murder hornet”. I wanted to use this example for a talk I had planned to give at a conference about “invaders”, animals that arrive from somewhere and stay (or die). I also wanted to talk about the confusion and uncertainties that exist with regard to terms like autochthonous, indigenous, endemic, native, etc. It really isn’t easy to say with certainty if a species has evolved in one location or has got there from another place from where it may ultimately have disappeared and, if so, whether the colonization was the result of an accidental transport by rafting, aided by the wind or ‘hitchhiking’ on birds. I got interested in this, because on Hachijojima, a volcanic Pacific island 300 km south of Tokyo, inhabited by people who until ca. 70 years ago had their own language, I noticed a multitude of species that shouldn’t have been there: rats, ferrets, cats, etc.

But what about the non-mammalian vertebrates: two snake species; one toad and 3 species of frogs (American bullfrogs, introduced after the 2nd World War, are probably now no longer residents on the island). How did they get there? Snakes were presumably deliberately introduced to kill mice. Attempts to eradicate the Japanese toad exist, but I think it’s already too well established. Then there is the firebelly newt, a harmless species that seems to have arrived in the early 1970s and (as we were able to show by molecular studies) from one place of origin in Japan with all individuals on the island related to each other. Maybe children (or a teacher) took some eggs or a few adults from Shikoku as pets to Hachijojima and released them. The newts are now everywhere, but nobody minds as they’re harmless and quite cute.

It’s a different matter with millipedes, thousands, nay millions of them! Most people hate them and say they stink; others see them as a nuisance as their crushed bodies make the road slippery and only a few gardeners tolerate (or even like them) as they do not attack healthy plants or fruit, but shredder dead plant material and help recycling it. They are known to have come from Taiwan in 2002.  Also, from Taiwan are the now widely distributed whip scorpions. And another immigrant from Taiwan was the terrestrial leech that I readily found when looking for it (it had never before been seen by locals or scientists who had been searching for it: probably because of its similarity to earthworms it was always overlooked). Unsurprisingly, two species of nematode worms that had hitched a ride as parasites in the millipedes were also recorded for the first time. A species of earthworm known from India turned out a new find and for the first time for Japan a Canadian freshwater limpet was recorded from Hachijojima by me. The freshwater crab Geothelphusa dehaani (a non-native) must have been introduced, because people eat it; fireflies, too, were deliberately introduced, but to attract tourists to the island. Slimy and alien earthworm-eating planarian flatworms, however, (I collected 4 species) would be less attractive.

But how come all these diverse alien creatures (surprisingly many from Taiwan) can survive and thrive on Hachijojima? The main reasons are:  Hachijojima even in winter does not experience frost; there is a lack of predators and Hachijojima has had a number of volcanic eruptions, some thousands of years ago, the last one (involving only the northern region of the island) 330 years ago. Such upheavals lead to species extinctions and create ‘spaces’ for new introductions. Finally, the surprising variety of habitats on the island meant that there are niches for a large number of alien arrivals. And they, in turn, allowed me to find “my niche” as a keen observer of Nature and her inhabitants while on this wonderful island!

© Dr V.B. Meyer-Rochow and, 2020.
Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and with appropriate and specific direction to the original content. 

biology zoology blog benno meyer tree bark

Spots or Stripes

Which is better?

This is the question I’ve never been able to answer correctly when going shopping to buy a blouse or a jacket with my wife. If I’d say the spots look nice, she’d reply, but what about the stripes? If I then say the stripes look even better, I get to hear “but they make me look fat”. If I then suggest a patchy kind of pattern, I get told that I’m of no help. Can animal coat patterns help in cases like these? Let’s examine.

Dots and spots are surprisingly common amongst predatory animals and the leopard immediately comes to mind. Leopard, ocelot and jaguar need to approach their prey unseen and during the day in or under trees, the changing patterns of shaded and sunlit patches (caused by the movement of leaves and vegetation due to the wind) renders them almost invisible. Hunting at night under moonlight would undoubtedly make it even more difficult to see them. The cheetah is also spotted, but does not live in the jungle or amongst dense vegetation and hunts during the day. Why isn’t the cheetah sand-coloured like a lion. Hyenas also have spots, but often they don’t even hunt at all; they steal the food from others.

Not all cat predators with spots are big: some smaller ones like housecats and the Australian quoll have spots, too. But tigers always have stripes, mostly vertical ones that is. It certainly makes it more difficult to spot a tiger when it is prowling around in high grasses.  It’s probably correct to say that dark and lighter spots or vertical stripes are a form of camouflage allowing a predator to approach its prey more easily. However, even prey may have spots or possess stripes. Fallow deer and, of course, bambis have spots, but the bovid species ‘bongo’ and the small antelope ‘zebra duiker’ possess vertical stripes just like zebras. The stripes of the latter, however, are not vertical on the legs but horizontal. Horizontal stripes along the body are typical of wild piglets and young tapirs, and even emu chicks, but would that help them to remain undetected? One should think that vertical stripes would be a better camouflage.

Snakes and lizards are long and slender and that is often amplified by horizontal lines along the body and tail. This would certainly make sense if there weren’t these crass exceptions: coral snakes and sea snakes are vertically striped, possessing red or yellow bands on a black background (or black stripes on a yellow or reddish background) which does not render them cryptic, but highly visible. But is it wise to be seen, to be recognized? I suppose if you are venomous and can defend yourself (and the attacker does not die, but would remember to leave that stripy fellow alone) it would be an explanation. To explain similar body colour patterns, Batesian and Müllerian mimicry come to mind. The skunk’s black and white coat has a similar message: ”I’m not an easy prey; don’t you remember that nasty lesson I taught you the last time you tried?” Most likely the immensely colourful spots and stripes of many tropical and venomous frogs and the black and yellow spots of salamanders are warning colorations too.

And under water? An enormous variety of colours, spots and stripes  –  but no single “unifying” rule. The most gigantic fish, the whale shark, has spots. But so have many puffer fishes and tiny box fishes, for example Ostracion cubicus. Freshwater fish like trout may have spots, but also some skates and the catfish Synodontis negrita, too. Another catfish, the slender Plotosus lineatus, has horizontal stripes, but many open water species and the cryptic moray eel Gymnomuraena zebra have vertical stripes. Many  tropical angel fishes have horizontal stripes. Some cichlids and the lionfish Pterois sp. have both spots and stripes. And the reason for this piscine kaleidoscope: the flickering and constantly moving shady and lit patches created by the waves and the movement of the water above (plus the coral habitat, rocks and bottom substrate). Does this knowledge help our lady (see the beginning) to decide whether to choose the spots or the stripes?  With clothes and women, you’ll never have a satisfactory answer.

© Dr V.B. Meyer-Rochow and, 2020.
Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and with appropriate and specific direction to the original content.