A Wealth of Rats

Robert M. Timm

Illustrations by Wendy Hollender


“Rats!”
   —Snoopy, in the cartoon Peanuts (January 1, 1967)


Introduction

Say the word “rats” and you invoke a variety of images in the minds of listeners. The Midwestern farmer thinks of stored grain that may be eaten or contaminated if these rodents get access to his bins and silos. The psychology student considers the albino lab rat that can be taught to press levers for rewards. The southern California homeowner finds rodent-eaten oranges on her backyard tree, and at dusk has watched a rat scurry along the telephone lines. The pet shop manager stocks young hooded rats for sale as pets, or as live food for those who own boa constrictors. The toxicologist uses laboratory rats to determine how their bodies metabolize potentially harmful compounds. The health department technician combs the fur of a rat that was cage-trapped at a major port facility, to make sure it or its fleas are not infected with plague.

Yet, all of these images originate with only two or three species of rats – the commensals – that are adapted to living in close association with humans and human resources, providing them food and shelter. Of rats worldwide, only a very few species are considered “pests” wherever they occur. Western society’s dislike of few kinds of rats has thus besmirched the reputation of an entire large and diverse group of rodents that happens to be called “rats”, either in terms of their taxonomy or by reason of their vernacular names. Many types of “rats” are not known to be of any great importance to people. They go about their lives, sometimes living in very specialized and limited natural habitats, having little or no effect on human activities.

What exactly is a “rat”? As recently as the mid-18th century, the word “rat” was defined as “an animal of the mouse kind that infests houses and ships” (Samuel Johnson's Dictionary of the English Language, 1755). The advent of modern scientific taxonomy, starting in the late 18th century with the standardized Latin binomial nomenclature developed by Linnaeus, allowed scientists to more easily differentiate one kind of animal from another. Yet, the term “rat” is used in the vernacular and has remained imprecise. “Rat” is applied to a number of rodents throughout the world, some of which, in terms of evolution, are not closely related to each other.

Our purpose is to take a look at the broad scope of rats and rat-like rodents found throughout the world, so as to gain a better appreciation of their diversity and uniqueness. In doing so, we include not only species of “true rats” (of the genus Rattus) but also animals that have been given common names such as “wood rat”, “kangaroo rat”, and “mole rat”. Some of the species we include are threatened or endangered, while others are numerous and widespread, and a few have come to be established world-wide. Some are highly specialized in terms of their habitat requirements, while others can survive or even thrive in a variety of environments. Some are little-known and poorly understood, while others are undoubtedly among the most thoroughly-researched species on the planet.

Each species we discuss is unique, and some have unusual adaptations. For example:

The Giant Kangaroo Rat, Dipodomys ingens, constructs soil “pits” or miniature haystacks for sun-curing seeds and seed heads it has gathered, so that when these foods are later stored in its burrows they will not mould or mildew.

The Greater Stick-Nest Rat, Leporillus conditor, builds nests of sticks that can be up to 5 feet (1.5 m) high. In Australia, when these nest structures were first discovered in 1838, they were thought to be made by Aborigines for lighting signal fires.

The Malagasy Giant Rat, Hypogeomys antimena, has muscular hind legs that enable it to jump nearly 3 feet into the air, helping it to escape predators.

The endangered Laotian Rock Rat, Laonastes aenigmamus, first discovered by Western scientists in 1996, has outward-splayed feet that permit it to travel over flat ground only slowly with a somewhat “duck-like” gait. This adaptation, however, is well suited for climbing up and across large limestone boulders, which serve as its principal habitat.

The Marsh Rice Rat, Oryzomys palustris, is highly susceptible to a bacterial disease of the teeth and gums, making it a useful model for the study of destructive periodontal disease in humans.

In addition to providing a brief natural history of each of the 35 species we have described, we also include discussions about the ecology and adaptations of rats and rat-like rodents; rats in art, literature, and culture; and rats in relation to human history. In doing so, we hope the reader will gain a broader appreciation of the fascinating rodents that are called “rats”.


Rights available: world


Specifications

160 pages
35 color illustrations
index
Dimensions: 6 x 8 inches

Gambian Pouch Rat – Cricetomys gambianus

Notable because of their large size, with adult males reaching a weight of up to 6.2 pounds (2.8 kilograms), this widely-distributed African species has made news several times within the past decade. As one of the world’s largest rats, its combined head and body length are usually in excess of 1 foot (30 cm), and including tail the total length can reach 31 inches (80 cm). They transport food items in their large cheek pouches, similar to the internal cheek pouches found in many kinds of ground squirrels.

It is difficult to distinguish this species from its nearest relative, Emin’s Pouched Rat Cricetomys emini; together, both species are known as “African Giant Pouched Rats”. C gambianus has coarser, browner fur and a dark mask around the eyes, while C. emini has a soft grey coat and a clean white belly. They also have different vocalizations: C. emini emits a long modulated call, while C. gambianus makes a short single cry. Where the two species live sympatrically, no hybridization has been found. Scientists currently do not know if interbreeding between the two species does not occur because they cannot communicate with each other, or if there are other (perhaps physiological) barriers.

Their native range includes tropical and subtropical Africa south of the Sahara Desert down to about 27 degrees south latitude, thus stretching from the West African countries east to Sudan and southwards into the Transvaal and the KwaZulu and Natal provinces of South Africa. They can be found in forests, guinea savannahs, open grasslands, and on rock grass-covered mountaintops, typically occurring in regions that receive in excess of 31 inches (80 cm) of rainfall annually. Intolerant of hot daytime temperatures, they are active primarily at night, and during the day they take shelter in elaborate burrows they have constructed. In heavy vegetation, however, they will use fallen trees or rotten logs, rock piles, termite mounds, or other animals’ burrows for shelter. On rare occasions when they have been observed foraging during daytime, they have been said to behave “as if almost blind, sitting on their haunches and sniffing in all directions”. When a pouch rat ventures out of its burrow, it is said to frantically rush around, picking up anything that looks possibly edible or interesting Cramming its cheek pouches full, it returns to its burrow, where it unloads it collected items and leisurely inspects each item, one at a time.

The pouch rats’ burrows or other shelters are typically comprised of long passageways with various side alleys and several chambers, one of which may be used as a sleeping place or breeding nest, while others are storerooms for cached food. When transporting food back to its burrow, a rat may make 10 to 100 round-trips over a time period spanning 30 minutes to 6 hours. In a single trip, a rat can carry a volume of about 6 cubic inches (100 ml) in its cheek pouches. In addition to transporting food items, Gambian Pouch Rats also exhibit a behavior similar to that of North American woodrats (packrats) in collecting shiny inedible objects, apparently selected for their bright appearance. Gambian Pouch Rat storerooms have been found to contain such items as pocket knives, bottle-tops, keys, pencils and pens, chalk, a silver earring, a blue glass marble, red cloth, rings, and in one case, 300 francs in coins.

They eat primarily plant materials and have a preference for nuts and kernels of the oil palm. Studies have found them to consume leaves, grasses, roots, tubers (yams, cassava), insects (ants, grasshoppers, and termites), corn and other seeds, and occasionally crabs and snails.

Their broad habitat and dietary tolerances allow them to adapt to various locations, including living in and near human habitation. In some West African locations, they have invaded sewer systems. They can thrive in towns and villages, where they use shrubs and hedges for cover and at night will raid vegetable gardens and refuse dumps. When they live near agricultural fields, they are known to cause significant damage to damage to beans, cassava, and peanuts (called “groundnuts” in Africa). In some areas, the rats are hunted as a food resource by local residents, who consider them a delicacy and have raised them in captivity as a cheap source of protein. In some areas of Central Africa, their skins are used as tobacco pouches.

A very interesting parasite lives on Cricetomys. This is a flightless cockroach, Hemimerus. One species, H. hanseni, is reported to feed on the stored food and debris in the rat’s burrow; but observations on another similar ectoparasite of the Gambian Pouch Rat, H. talpoides, found that they fed only on the rats’ body secretions. When present, seven or eight of these insects typically live on each rat.

Gambian Pouch Rats first made news in the U.S. in 2003, when a shipment of various rodent species from Ghana imported into the pet trade were housed adjacent to prairie dogs, which subsequently resulted in humans being infected with monkey pox virus, known to be of African origin. Reports of this disease in Gambian Pouch Rats caused a drop in their demand as pets. Additionally, news of the disease outbreak led residents Florida to report to authorities the presence of Gambian Pouch Rats on Grassy Key. Subsequent investigations revealed a thriving population on both Grassy Key and Crawl Key, which apparently resulted from the escape of 8 animals from an exotic pet breeder on Grassy Key in 1998 or 1999. Since that time, the U.S. Department of Agriculture in cooperation with local authorities has undertaken an effort to eradicate the pouch rats from these two islands, as the rats were considered to be a major potential threat to agriculture, should they continue to spread onto mainland Florida and throughout the south-eastern U.S.

About the same time, Belgian engineer Bart Weetjens came up with the idea of training Gambian Pouch Rats to detect land mines. Because of their excellent sense of smell, intelligence, and ability to be trained, this concept has now developed into a successful program currently in progress in Tanzania and Mozambique. Breeding colonies have been established, and a rat begins it training at the age of 5 weeks, after having been weaned. A positive reinforcement method known as clicker training is use: when the animal responds to the scent of explosive chemicals in soil, the trainer clicks a small handheld noisemaker before giving the rat a piece of banana or a peanut as a reward. Most rats complete their training in between 6 to 10 months, and a cadre of these “HeroRATS” have been tested and accredited by the Geneva International Center for Humanitarian Demining. A rat and handler can search about 180 square yards (150 square meters) in half an hour. As compared to mine-sniffing dogs, which had been used previously, Gambian Pouch Rats are cheaper to train and certify (about $2,000 per rat, compared to about $12,000 per dog); they are easier to maintain and transport to and from field sites; they are not heavy enough to detonate mines in the field; they are less subject to tropical diseases; and they are less emotionally tied to people, thus making it easier to transfer them between handlers.

Weetjens’ humanitarian research organization APOPO is also evaluating the ability of trained Gambian Pouch Rats to detect the presence of tuberculosis in human sputum samples. This disease is a major public health concern in Tanzania and throughout Africa, and the standard microscopic laboratory analysis is slow (a technician can evaluate a maximum of 40 samples per day) and inaccurate. Preliminary research, done in Tanzania in conjunction with Sokoine University of Agriculture, has shown that the trained rats are potentially more reliable, faster (a rata can analyze 100 samples in about 20 minutes), and therefore more cost-effective in detecting TB-infected samples.

Giant Kangaroo Rat – Dipodomys ingens

The Giant Kangaroo Rat is the largest of more than 20 species of kangaroo rats. In adults, the body is about 6 inches (15 cm) in length, not including its 7 to 8.5-inch (18–21.5-cm) tufted tail. Kangaroo rats all are all found within the genus Dipodomys, and they are native to dry habitats in western and central North America. While not closely related, they have evolved similar adaptations to living in sandy, arid climates as have jerboas (found in the deserts of north Africa and Asia) and hopping mice (in Australia).

The Giant Kangaroo Rat has been listed as Endangered in the U.S. since January 1987, with rapid loss of its habitat believed to be the principal reason for its decline. Historically, it was found throughout a band of gently-sloping land along the western edge California’s San Joaquin Valley. During the 1970s, almost all the natural communities on the western floor and gentle western slopes of the Tulare Basin were developed for irrigated agriculture, thus making the habitat unsuitable for kangaroo rats and a number of other native species. Expansion of development for petroleum exploration in the area, accompanied by the growth and spread of a number of small cities and towns in the area, also contributed to habitat loss. Land use changes are thought to have displaced the species from much of its prime habitat into marginal shrub-dominated areas and hillsides. By the late 1990s, it was estimated that the Giant Kangaroo Rat’s occurrence has been reduced to approximately 3% of its historic range, now fragmented into 6 geographically distinct areas.

Giant Kangaroo Rats are primarily solitary and nocturnal. Typically, they emerge from their burrows soon after sunset and are active for a total period of about 2 hours. During this time of foraging for seeds and other foods, they are briefly active at the surface, but they soon retreat to the safety of their underground burrows. All together, any single animal is active aboveground only for about 15 minutes per night. There are, however, occasions when Giant Kangaroo Rats have been seen above ground during daylight, including midday in the hottest part of the year. During nightly foraging, they gather individual seeds scattered over the ground’s surface and mixed in the upper layer of soil. They use texture to differentiate seeds from soil particles, but when soil particles are coarse, their ability to efficiently identify and collect food decreases dramatically. Thus, they prefer the finer soils present in areas that now recognized as “prime” habitat, but recently converted to agricultural crop production.

Giant Kangaroo Rats will cut the ripening heads of grasses and forbs and cure them in small surface “pits”, which they construct on areas over their burrow systems. These surface pits are uniform in diameter and depth (about 1 inch, or 2.5 cm), placed vertically in firm soil. Pits are filled with the contents of the kangaroo rat’s cheek pouches, after a single trip to harvest seeds. After placing seeds and seed heads in the pits, the animal covers them with a layer of loose, dry dirt. After the seeds in the pits become sun-dried, they are then moved into the kangaroo rat’s underground burrow for storage. Sun-drying prevents subsequent molding and spoilage of the seeds. To sun-dry the seeds, some Giant Kangaroo Rats will also make large stacks of seed heads on the surfaces of their burrow systems, but this behavior is seen only in some populations and not in others.

The ability to transport large quantities of seeds and other food, and their highly developed food caching behaviors, coupled with relatively high longevity of adults with established burrow systems, probably allows Giant Kangaroo Rats to endure severe drought for 1 or 2 years without great risk of population extinction.

A Giant Kangaroo Rat’s burrow is shallow, but deep enough for it to escape the afternoon heat and avoid predators. Burrows have two to four entrances that often surround a bush or shrub. A mound of soil at the base of the plant and numerous tracks in the immediate surrounding area may be seen near burrow entrances. While individual animals use and defend territories, the core area of use, located over the burrow system, is the most intensively-used part of the territory and is termed a “precinct”. Recent studies indicate that multiple individuals, most likely family groups of females and offspring of different ages, may live in precincts. Depending on habitat quality, which can vary with location as well as amount of annual rainfall, density of Giant Kangaroo Rats can range from 1 to 44 animals per acre (1–110 per hectare).

Like other kangaroo rats, the Giant Kangaroo Rat communicated with others of its species by rapidly drumming the ground with its elongated hind feet, apparently for the purpose of declaring ownership of its territory. Compared to other kangaroo rat species, the Giant Kangaroo Rat has the longest drum roll, which is applied with greater tolerance, compared to other kangaroo rat species, before actual physical conflict is initiated.

When originally seen and described by the pioneer mammalogist Joseph Grinnell, Giant Kangaroo Rats were found to dominate the community to the exclusion of other rodent species. While they seem to be much more aggressive to other types of rodents than are other kangaroo rat species, it is no longer unusual to find them sharing habitat with two other species, the Heermann’s Kangaroo Rat (Dipodomys heermanni) and the San Joaquin Kangaroo Rat (Dipodomys nitratoides). Possibly, this change in behavior is due to their now occupying non-optimal habitats, as a result of human activities within their historical range.

The Giant Kangaroo Rat, by its relative abundance and burrowing activity, is a “keystone species” in grassland and shrub communities; that is, this species’ activities and presence have significant effect on multiple other species that live in the same habitat. Their burrows also are used by blunt-nosed leopard lizards (Gambelia sila) and San Joaquin antelope squirrel (Ammospermophilus nelsoni), both also classified as Endangered species. On the Carrizo Plain Natural Area, the endangered California jewelflower grows primarily on the burrow systems of Giant Kangaroo Rats. In spring, the kangaroo rats’ precincts are visible as distinct, evenly-spaced dark green patches, because of the more lush growth of herbaceous plants when compared to adjacent areas with less kangaroo rat use. In years when rainfall is sufficient to promote growth and fruiting of plants, the net productivity of herbaceous plants is 2 to 5 times greater on precincts than in surrounding areas. Further, growth of herbaceous plants on precincts was found to contain about 4 percent more protein than plants from surrounding ground.

In the changed habitat that now supports the remaining populations of Giant Kangaroo Rats, complete protection of the landscape or “turning back the clock” in an ecological sense are not feasible or even desirable strategies to protect this endangered rodent. For example, vegetation that becomes too dense will exclude these kangaroo rats, possibly because it interferes with their ability to visually detect approaching predators on moonlit nights. Scientists now understand that lack of grazing or fire to control density of vegetation (including shrubs), surprisingly, may be a threat to Giant Kangaroo Rats. The recovery plan for this Endangered species even recommends that within certain parts of the Giant Kangaroo Rat’s habitat where livestock grazing no long occurs, it should be reestablished. While fire can be beneficial to the habitat, uncontrolled fire that occurs at the wrong season or in the wrong area could also have negative consequences for Giant Kangaroo Rat survival.

It is now known that introduced grass species such as red brome (Bromus rubens) help support population stability of the Giant Kangaroo Rats: their seeds are considerably larger than those of native plants, and thus easier for the rodents to find in gather in coarser soil conditions where they now often live. The relationship with this non-native grass is of mutual benefit, because as the Giant Kangaroo Rat disrupts the soil, it assists the germination of this invasive grass. Protecting native plants unable to compete with this invasive grass is then difficult, because it compromises protection of the Giant Kangaroo Rat.

While Giant Kangaroo Rats are a major prey items for many predators, the kangaroo rat’s reproductive rate (with litter sizes of typically 4 to 6 young, which is high for most species of kangaroo rats), is quite adequate to compensate for normal levels of predation or even to permit population recovery. Further, one of the kangaroo rat’s predators is itself an Endangered species, the Lower San Joaquin kit fox (Vulpes macrotis mutica).

While the Giant Kangaroo Rat remains endangered, scientists have sufficient knowledge to manage its remaining habitat successfully and for its benefit. The major continuing threat is that not all of its current range is protected again further habitat change, the principal threat to its continued existence.


Greater Stick-Nest Rat – Leporillus conditor

The Greater Stick-Nest Rat gets its common name because this native Australian rodent constructs large nests of sticks, primarily as a means of providing shelter and a defense against predators. European explorers who first encountered these piles of sticks first assumed they were built by Aborigines for use in lighting signal fires. subsequent explorers and naturalists, however, recognized that these stick structures, being similar to the nests built by packrats (Neotoma species) in North America, were built by rodents. Some observers provided considerable detail their findings. For example, Charles Sturt in 1848 wrote, “The nests they construct are made of sticks varying in length from three inches to three feet, and in thickness from the size of a quill to the size of the thumb. They were arranged in a most systematic manner, so as to form a compact cone like a bee-hive, four feet in diameter at the base and three feet high. This fabric is so firmly built, as to be pulled to pieces with difficulty. One of these nests had five holes or entrances from the bottom, nearly equi-distant from each other, with passages leading to a hole in the ground, beneath which I am led to conclude they had their store. There were two nests of grass in the centre of the pyramid, and passages running up to them diagonally from the bottom. The nests were close together but in separate compartments, with passages communicating from the one to the other. In a pyramid that we subsequently opened, there was a nest nearly at the top…”.

When Greater Stick-Nest Rats construct their nests in areas where there is little woody vegetation available, they will pile loose heaps of sticks over rabbit warrens, which allow quick escape from predators. These stick piles often have small stones placed on top of, or among, the sticks, which anchor the structures against strong winds. In areas near the ocean where large nests were constructed out on the flats, it has been noted that sometimes they were placed over the burrows of penguins.

Greater Stick-Nest Rats somewhat resemble small rabbits in size, having blunt noses, large ears, and body fur described as “fluffy” or “sleek”, and grow to be up to 10 inches (26 cm) in length and weigh up to 1 pound (450 grams). European colonists to Australia called them “rabbit-rats”, while their Latin genus name, Leporillus, is derived from the Latin ‘lepus’ for hare, and ‘-illus’ implying diminutive size. They are described by one source to be “gregarious … gentle and tame, even when freshly caught, and are reminiscent of little rabbits with long tails” (Ride 1970). Others have observed, however, that they can show aggression among themselves, establishing dominance hierarchies within their social groups.

Called “wopilkara” by the Aborigines, they were featured regularly in the diets of these native Australian peoples. Early explorers and settlers also found the rats easy prey and “sport”. Krefft (1866) described their flesh as “white, tender and well-tasted”. Ernest Giles (1889, cited in Copley 1999) also claimed that “their flesh was very good eating”, while Maurice (R. T. Maurice, 1897, unpublished autobiography, Mortlock Library, cited in Copley 1999) noted that these animals “although small are very delicious when made into a curry”.

Greater Stick-Nest Rats are exclusively herbivorous and eat leaves and fruits of succulent plants such as bluebush and saltbush. Their original distribution was quite wide, extending from the western edge of New South Wales through much of South Australia and across Western Australia in a band from just north of Perth up the western coast to Onslow.

In the Murray/Darling region, the rats primarily inhabited the alluvial terraces of the floodplain, which was dominated by river saltbush (Atriplex rhagodioides) and/or black bluebush (Maireana pyramidata) and/or nitre-bush (Nitraria billardierei) shrublands. These areas were among the first and most negatively affected by introduced livestock, particularly sheep. In the Flinders Ranges, evidence suggests Greater Stick-Nest Rats were probably extinct from the region by the 1870s–80s, when the introduced European rabbit first arrived and became established there. In central Australia, including many locations where livestock were not introduced or widely grazed, however, the decline in Greater Stick-Nest Rats (as well as in a number of other native species) appears to have followed the establishment of rabbits during the 1890s and early 1900s. There, the Greater Stick-Nest Rat apparently was able to co-exist with the rabbits for 20–30 years or more, though often at seriously reduced abundance, and then they crashed to extinction quite suddenly. In some areas, native rodent numbers crashed soon after the establishment of introduced European red foxes (Vulpes vulpes). By the 1930s, the Greater Stick-Nest Rat, as well as its closest relative, the Lesser Stick-Nest Rat (Leporillus apicalis), were extinct on the Australian mainland. Subsequently, a remnant population of Greater Stick-Nest Rats was discovered on the Franklin Islands in Nuyts Archipelago, off the coast of Ceduna, South Australia, by Professor Wood Jones. He noted that the rats were living independently of fresh water supplies, but that the staple item in their diet was the succulent Tetragona implexicana, which they ate in “huge quantities”. He also found, however, that he was unable to attract them into traps with any type of bait.

Although historical records of the decline and extinction of these species are fragmentary, scientists now believe that habitat degradation (i.e., severe reduction in both vegetation cover and productivity) by livestock and other introduced herbivores appears to be the only common factor in local extinctions of Greater Stick-Nest Rats across their ranges. Severe droughts that occurred during the same time period likely prevented their declining populations from recovering, but they were not the main cause of the declines. Similarly, predation is thought to have significant secondary reason for the demise of the Greater Stick-Nest Rats. In addition to the introduced foxes and domestic cats, the rats were also known to be prey for several native predators (including the barn owl, Tyto alba; the western quoll Dasyurus geoffroii, also known as the chuditch or ‘western native cat’; and perhaps the dingo, Canis lupus dingo). Depletion of vegetative cover likely increased impacts of predation: these are relatively large rats with a principally herbivorous diet, thus their food source is relatively low in nutrients, causing them to spend a considerable amount of time foraging. Thus, reduction in food resources necessitated that they spend more time in activities that exposed them to predation.

Following the formal declaration of the “Endangered” status of the Greater Stick-Nest Rat in the 1980s, conservation and recovery plans were put in place to protect the last remaining populations of the species, found on the Franklin Islands. A captive breeding and rearing program was begun from animals taken off these islands and since 1990, new populations have been established on 3 additional islands and at 4 mainland sites. Currently, viable and sustainable populations are considered to exist at only 5 of 8 locations. Due to the success thus far, the status of the species has now been downgraded to “Vulnerable”, but it still remain at risk because of limited numbers and distribution, and from threats such as predators, severe drought, extensive fire, competition with introduced rodent species, and disease. While the reproductive capacity of this species is not as great as other species of rodents (1 to 3 young are born after an unusually long gestation period of 44 days) females can breed all year and are capable of producing 2 or 3 litters annually. Thus, given some degree of continued protection, the prognosis for this species’ survival in the wild looks encouraging. Unfortunately, its closest relative, the Lesser Stick-Nest Rat (Leporillus apicalis), also called the White-Tipped Stick-Nest Rat, has not been seen since 1933 and is considered to be extinct. It apparently occupied similar habitats, often in sympatry with L. conditor, but extended its range further into the arid zone and may have had a more arboreal life-style and a more diverse diet, including invertebrates.

In attempting to discern the original distribution of Greater Stick-Nest Rats, Peter Copley and his colleagues researched records of early explorers and naturalists; sought museum specimens to verify the locations of collection, where it was recorded; sent questionnaire to pastoral landowners in regions where the species were thought to have existed; and in the 1980s interviewed the older members of Aboriginal groups for recollections and personal knowledge of the existence of the species, using museum study skins and fragments of Greater Stick-Nest Rats as aids to help these elders recall information. Fortunately, remains of stick-nests (termed “wurlies” in Australian idiom, after the name for the Aborigines’ temporary shelters built of tree branches) still occur over a wide area of arid and semi-arid Australia. Nearly all of these nest remnants are found beneath rock overhangs in breakaway cliffs, or in caves, where they have received protection from rain and from wildfires. In such situations, many nests were occupied by generations of rats and, according to Copley’s observations, some nests became very substantial structures, up to 16½ ft (5 m) across and 6½ ft (2 m) high.

The continuous deposition of Greater Stick-Nest Rats’ urine and feces within their nests and on adjacent rock ledges led, over many years, to accumulations of a dark “bituminous” deposit termed cave bitumen or amber-rat. This substance is soluble in water, so the locations where such accumulations persisted were those in nest remains protected from exposure to water in the form of rainfall or seepages. Over time, the amber-rat solidifies to form a resin-like material that can last for thousands of years. Because the Greater Stick-Nest Rats, like their North American counterparts the packrats (Neotoma species), have a behavioural tendency to collect and hoard various objects within their environment that draw their attention, investigators have found within these amber-rat deposits pieces of bones, hairs, egg shell fragments, raptor pellets, and carnivore droppings. Scientists studying these accumulations have concluded that Dasyurids appear to have contributed a large proportion of the hair and bone material to the nests studied, either directly during use of the nest, or indirectly through the collection of their scats from nearby by the Greater Stick-Nest Rats.

The amber-rat in these nests has thus often helped to preserve, in sequential layers through time, both the various items brought back to the nest by its inhabitants, but also the plant fragments used in construction of the nest structure and to line its various chambers. Additionally, the sticky surface of the amber-rat also attracts and traps airborne pollens, which provide additional information on the region’s flora. North American scientists studying the similar nests of packrats have thus been able to reconstruct paleo-botanical histories of the region, aided by the ability to carbon-date the contents of these rodent nests. They have coined the term “packrat middens” for such structures, which have come to be recognized as treasure-troves of information about vegetation changes that have taken place over the past several thousand years in arid and semi-arid zones. Of the Greater Stick-Nest Rat middens studied thus far, some have been occupied by rats from the recent past (200–300 years ago), but others have been aged to a period that extends back several thousand years. So far, the oldest nest midden in Australia was estimated to be approximately 10,800 years old. In a relatively new and exciting development, preliminary data from middens as old as 4,000 years from Queensland, New South Wales, and Western Australia have demonstrated that DNA surviving in these deposits and can be extracted, amplified, and identified, providing an additional tool to understand how plants, animals, and communities have changed through time. Thanks to Greater Stick-Nest Rats, the paleo-environmental record in Australia over the past few thousand years has been preserved in these rodents’ middens, providing a valuable source of information about short-term climatic shifts as well as long-term ecological changes, which may in the future affect humans as the world’s climate continues to change.


Robert M. Timm is Staff Research Associate, Department of Wildlife and Fisheries Biology, University of California Davis. His work focuses on wildlife-agriculture interactions; prevention and control of conflicts between wildlife and human activities; behavior and management of coyotes; and behavior and control of rodents.

He is recipient of the “Outstanding Book” Award for editing Prevention and Control of Wildlife Damage, presented by Natural Resources Council of America, Washington D.C.


Wendy Hollender is the coordinator for Botanical Art and Illustration at The New York Botanical Garden. She had designed textiles for more than 20 years. Through her work developing floral designs for clients such as Wedgwood China and Westpoint Stevens, she became intrigued with the complex beauty of plants.

This fascination inspired Hollender to earn a certificate of Botanical Art and Illustration, and become a full time botanical artist and illustrator. Since 2002 her work has focused in this area.

She is the founder of WH Art & Design, which focuses on original botanical artwork for a variety of uses, including museums and conservation groups. Some of her clients include: the French beauty company Coty Inc., the Riverside Park Fund, the Morven Garden and Museum, the Nantucket Conservation Foundation, Faber-Castell Inc., and the New York Botanical Garden.

Hollender is a graduate of the Rhode Island School of Design. She teaches students at the New York Botanical Garden, the Brooklyn Botanic Garden, and leads workshops in locations such as the ASA Wright Nature Preserve in Trinidad and the National Tropical Botanical Garden on Kuaii, Hawaii. She has taught at the Yale University Center for British Art, Grinnell College, Wellsley College and the San Francisco Botanical Garden. She also teaches a yearly workshop for high school students in the south Bronx teaching botany through botanical drawing.


Exhibitions:

Hollender’s work will be part of the 2010 exhibition at the Hunt Institute for Botanical Documentation at Carnegie Mellon University. Her work has been exhibited at the New York Horticultural Society and the Brooklyn Botanic Garden. Her newest solo exhibition was at the Interchurch Center Corridor Gallery in April 2009. Recent solo exhibits have been: “Riverside Park and Beyond” at the Interchurch Gallery in New York City Spring 2006, and” Coastal Botanicals, from Nantucket and Beyond” at Wellesley College December, 2005. She exhibited at the Royal Horticultural Society of London in February 2007 where she was awarded a silver medal.


Publications:
In January of 2008 Wendy published Botanical Drawing, A Beginner’s Guide, a workbook for anyone who wants to learn Botanical Drawing. It has been selling steadily at the New York Botanical Garden, the Brooklyn Botanic Garden, The Getty Museum, the Smithsonian Institute and on the artist’s website.

Her new book: Botanical Drawing in Color is being published by Random House in July, 2010.

She is a member of the American Society of Botanical Artists, the Guild of Natural Science Illustrators,and the Brooklyn Botanic Garden Florilegium Society. Hollender is also a member of corporation at The New York Botanical Garden and on the board of the American Society of Botanical Artists.


 

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