Gazelle articles September 1999

Contents:

Fair Weather Friends: No Zygonyx

Zygonyx torridus is a medium to large size, dark blue-black dragonfly that patrols over running water in mountain wadis, seldom perching for observation but distinctive by its behaviour. Found in tropical and subtropical Africa, Arabia and east to Pakistan and India, it was added to the UAE list by Graham Giles in 1997 and was seen here regularly during the winters of 1996-97 and 1997-98. However, it was not reported at all during the 1998-99 season, presumably due to the absence of sufficient rain.

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High Fliers

Where to go to beat the summer heat? Gary Feulner and Barbara Couldrey went as high as they could get in early August, camping at 1500 meters in the Ru'us Al-Jibal, above Khasab in the Musandam Peninsula. Alas, a good night's sleep still did not come easily, they said, due to a combination of warmth and wind. Hiking, on the other hand, proved very successful (with a 5:00am start). They reached the summit of Jebel Mintera (1880 meters) by 9:00am and agreed that coming back down in the midday heat was harder than the ascent.

At the top they were surprised to find several large Emperor-style dragonflies patrolling the football field sized summit plateau. Gary tentatively identified them as Hemianax ephippiger, the Vagrant Emperor, but this species is notoriously difficult to distinguish in the field from Anax parthenope, the Lesser Emperor. Both are strong migrants. Gary wondered if they might be "hill-topping," like butterflies, in order to find others of their kind. Graham Giles, who has published a checklist of the dragonflies of the UAE, speculates that they may have stopped at a good food source in the course of migration. Or maybe they, too, were just trying to beat the heat.

Also seen unexpectedly were several Leopard butterflies (Apharitis acamis), both near the summit and near camp. This species is rare in Arabia, and is discussed in a note by Dr Michael Gillett of Al-Ain in the latest issue of Tribulus (vol 9.1, Summer 1999). It lays its eggs in the trunks of palm trees, where the larvae feed on and/or are fed by ants that live there in burrows made by the larvae of the Rhinoceros beetle (Oryctes spp). Partly as a result, most recent sightings have been in mature date palm plantations in oases. Thus Mike Gillett was surprised to find a number of Leopard butterflies in March 1999 in scrub desert near Sharjah University City. The sightings high in the Ru'us Al-Jibal appear to be equally anomalous, since date palms, although not absent from scattered agricultural plots, are in relatively short supply.

No specimens were taken and the upperside was never well observed, but from the vivid orange colour that could be observed, it is speculated that the Leopard butterflies seen belonged to the Indian subspecies A. a. hypargos. Interestingly, Mike Gillett complained that his Sharjah Leopard butterflies seldom perched, and if approached they flew off too fast for the eye to follow. In contrast, those seen in the Ru'us Al-Jibal typically perched on low vegetation (perhaps to avoid a moderate breeze), flew only short distances if disturbed, and could be approached for photographs. Barbara in fact managed several times to perch one of the butterflies on her finger.

Barbara and Gary noted with mixed emotions the march of progress, even in the Ru'us Al-Jibal - new tracks, new agricultural plots, and even, on a high ridge, a modern steel animal trap (baited with lard) where once only stone traps were known.

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Camel Domestication

At the DNHG's festive end-of-the-season dinner in June, one of the quiz questions asked "How many animals have been domesticated in the last 4000 years?" The "correct" answer, according to the Internet site from which the question and answer were taken, is "None." Members may question, however, whether this answer takes account of the Arabian perspective. It is generally acknowledged that the dog, cat, horse, cow, donkey, goat, sheep, pig, chickens - all the common "barnyard" animals of Western experience - were domesticated by about 6000 years ago. Asians substituted yak and water buffalo. Reindeer are thought to have followed somewhat later. A good summary is found in Jared Diamond's Guns, Germs, and Steel: the Fates of Human Societies (W W Norton, 1997), Chapter 9. More recent attempts to domesticate animals such as the zebra or the fox (and other commercial fur-bearing mammals) cannot be said to have been successful.

But the camel is another story. Evidence for the domestication of the Arabian camel (or dromedary) before 2000 BC remains a matter of at least some debate, and the UAE is one of the places where positive evidence continues to be sought, since domestication is believed to have occurred first in South Arabia. Camel bones and representations of camels have been found in modest numbers in archaeological excavations from the Umm Al-Nar period (mid to late 3rd Millennium). Although not conclusive, this is generally taken as evidence of domestication by most experts, partly because the thriving economy of the Umm Al-Nar civilisation is thought to have been based to a great extent on the export of copper from the Hajar Mountains via the Arabian Gulf, and the camel is the most obvious means of transport that could have been used. Nevertheless, the first incontrovertible evidence of camel domestication is seen locally only in excavations from the Iron Age, beginning in the mid-2nd Millennium. Domestication at the latter date is corroborated by evidence from elsewhere, including Persia and Mesopotamia.

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Viper Strikes Out

Poisonous snakes are often thought of as the ultimate in efficient predators. Recent observations are a reminder that nobody's perfect, however. On a hot July morning Gary Feulner and Neil Curtis encountered a very small (c. 25 cm) carpet viper (Echis coloratus) on a bank of cobbles next to a long shallow pool near Wadi Jizzi. Reacting to the attention, the snake adopted its characteristic "folded" defensive posture.

While Gary and Neil were communicating this discovery, the snake struck a medium sized wadi toad. After a momentary tussle the two were motionless, the snake grasping the toad by the right thigh. Then suddenly the toad leapt free and into the water. Terrestrial vipers often voluntarily release small prey, who rapidly weaken and succumb to the effects of the venom. The snake then tracks the prey the few meters or tens of meters necessary, using its forked tongue and vomeronasal chemical sensing system. This strategy is problematic in the local context, however, since toads typically head for water to escape danger and the carpet viper is believed to avoid entering water. A toad released from the viper's grasp is therefore likely to be a lost meal.

The toad in question was watched carefully at first on the assumption that it would soon show signs of envenomation and die, but instead it seemed to recover, swimming, hopping and climbing. Observation was interrupted after about two minutes, however, when the snake unexpectedly darted its head back under the cobbles from whence it had first appeared, and emerged with a second, slightly smaller toad held just forward of the right hip. Gary and Neil had the impression that this second toad, somewhat dry and dirty, had already been stricken and somehow cached by the snake. But suddenly, once again, the apparently moribund toad seized its moment and escaped from the snake's jaws and into the pool.

After floating motionless for 15 or 20 seconds, the second toad, too, seemed to revive, and for at least two minutes thereafter it was able to swim and hop vigorously in order to escape manipulation. In hindsight, Gary and Neil wished that they had continued to watch both toads at greater length in order to confirm absolutely that they did not succumb to the venom, but instead they returned their attention to the snake. However, the initial reactions of both toads were suggestive of recovery.

This episode raises many questions. How did the toads manage to escape? Were they both too big for a small snake to hold in its jaws? It seemed doubtful that the larger of the two could have been swallowed successfully. Was the snake distracted by the human observers? And why was the snake's venom (apparently) not effective against these toads? Echis venom is notoriously toxic and experts caution that even baby vipers can be dangerous to humans. Or did the snake not inject its venom? Some medical and first aid literature says that in the case of human snakebites, vipers inject venom less than half the time. If not, why not? Were these really attacks at all, or do young vipers sometimes "practice" hunting like young mammalian carnivores?

More provocatively, if the snake must maintain its hold on a toad in order to succeed, what's the point of injecting venom at all? (Gary adds that in the only instance when he has witnessed the transition from impalement to ingestion, the snake never released its grip on the toad, but shifted its jaws forward in a series of methodical movements to put the victim in a head first position for swallowing.)

One otherwise plausible hypothesis that can be ruled out is that the toads proved unpalatable to the snake. Many toads produce powerful toxins exuded through their skins, and are avoided by most predators. Local toads apparently do the same and are reportedly shunned by domestic dogs and cats (at least after a first experience). However the carpet viper is well known to consume toads.

Alternatively, had the snake used up its venom in other recent unsuccessful attacks? If so, was this because it was especially hungry and striking indiscriminately? Is this why it was hunting as late as mid-morning? Or was it malnourished and unable to produce proper venom?

A final possibility is that the local wadi toads are somehow immune to the venom of the carpet viper. Since field observations indicate that these toads form a significant part of the diet of carpet vipers, it would be surprising to learn that the snakes may rely, and perhaps must rely, only on low-tech methods to catch them.

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UAE Flora Research

Ian Curtis, an Edinburgh resident and DNHG correspondent, eased the budget crunch in the natural sciences last winter by working as a volunteer researcher at the Royal Botanical Garden, Edinburgh. Those interested in the flora of the UAE, and the northern Emirates in particular, are the beneficiaries. Highlights of Ian's work have been reported in the Gazelle from time to time. This summer he completed a full report on the identification of specimens collected during his extended visits to the UAE, which demonstrates the progress that can be made with the proper resources and a determined effort.

As Ian tells it, "It was a very good learning experience working at the Herbarium. I didn't really know what I wanted to do, other than learn something about how it worked, and on the first day Tony Miller [A G Miller, co-author of Flora of Arabia, vol 1] handed me my pile of specimens from the UAE (donated earlier) and said, 'There you go. You may as well start by identifying that lot. . . .' A somewhat daunting prospect, especially as I thought I'd taken them about as far as I could while I was in Sharjah [at the herbarium of the Sharjah Natural History Museum, where Ian had a temporary appointment], though with the help of a binocular microscope, the massive Herbarium collection and the well stocked library I was able to sort most of the specimens out with not too much trouble. Some were very difficult, but I think all determinations are pretty accurate. Tony Miller has had a look over the list and was in agreement with what I came up with. . . . I hope the results contribute something to the knowledge of the UAE flora. I think there will be quite a few new names, though not necessarily new species, and several questions will have been answered. I wonder how many more could have been answered if I'd brought back more material!"

Ian has a particular interest in grasses, which most amateurs find difficult (DNHG Vice Chairman Valerie Chalmers is an exception), and his list includes many grasses from mountain environments. And despite Ian's disclaimer, he does seem to have identified a number of species new to the UAE, although not necessarily new to Arabia. Even among the "known" there were surprises. Among non-grasses, for example, he has distinguished two species of Polygala and two of Grewia where before only one each was recognised, and he has provided tips for identification.

Our thanks are due to Ian and to A G Miller and Marijcke Jongbloed for supporting and encouraging him.

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The Red Fox

The Commission of Environmental Research (CER) is to carry out a survey to discover the size of the red fox population on Masnoaa Island off Abu Dhabi. The island belongs to the Emirates Heritage Club.

Masnoaa, which literally means handmade or manufactured, is made of dredge materials, is shaped like a horseshoe, and covers 1.4 square kilometers.

Researchers will be trying to discover how the foxes came to be on the island in the first place. Did they arrive with stone from Ras Al-Khaimah when a breakwall was being constructed, or did they swim across from nearby islands when their own habitat was being threatened?

The once barren, flat and sandy, Masnoaa now has date palms and these foxes eat fruit as well as enjoying crabs and birds They take water from the irrigation lines but get most of their water from their food.

The survey will start later this year when researchers will attempt to trap and tag the foxes before releasing them back into the wild.

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