Meriones Crassus Research Articles

Pineal System of Desert Rodents and its Relationship to the Epithalamus

The morphological relationships of the pineal complex to the epithalamic structures have been examined at light microscopic level in five desert rodent species, Meriones crassus, Meriones lybicus, Gerbillus gerbillus, Psammomys obesus and Ctenodactylus vali. The pineal complex is classified as type ABC in M. crassus and G. gerbillus, AC in M. lybicus, AbetaC in P. obesus and alphabetaC in C. vali. In these rodent species, the pineal is an elongated organ which is dumbbell-shaped in G. gerbillus and M. lybicus, and extends above the cerebral hemispheres in M. crassus, leaf-shaped in P. obesus and lancet-shaped in C. vali. In P. obesus, pigment-containing cells are noted in the superficial part of the gland. In all species examined, the suprahabenular recess which is an extension of the choroid plexus of the third ventricule establishes a close anatomical relationship with the deep pineal. In C. vali, the suprahabenular recess is also contiguous with the pineal stalk and the superficial pineal component. In M. lybicus, M. crassus, G. gerbillus and P. obesus, a prominent dorsal vessel, the vena cerebri magna, intervenes between the suprahabenular recess, the superficial portion and the stalk. The most striking feature noted in this study is the presence of numerous melanocytes in the connective tissue capsule of the pineal gland, in the connecting stalk and in the connective tissue core of the highly convoluted suprahabenular recess in M. lybicus and M. crassus. The location of melanocytes in the restricted pineal area may suggest that these cells have a morphosignificance in photoreception or photoprotection.

Evidence for a negative fitness−density relationship between parent density and offspring quality for two Xenopsylla spp. parasitic on desert mammals

We tested the hypothesis of negative fitness-density relationships and predicted that an increase in the density of parent fleas would result in lower survival rates and longer development time of pre-imagoes as well as shorter time to death from starvation of newly emerged imagoes. These predictions were experimentally tested on Xenopsylla conformis Wagner and Xenopsylla ramesis Rothschild feeding on two rodent species, Meriones crassus Sundevall or Dipodillus dasyurus Wagner. Survival of larvae and pupae, but not eggs, was negatively affected by parent density. An increase in parent density led to a decrease in the number of imagoes of the next generation. Eggs of both species developed faster when the parents were at low densities on either host. The same was true for larval X. ramesis, but not larval X. conformis. The negative effects of parent density on the duration of pupal development were evident in X. conformis, parents of which fed on both hosts, and X. ramesis from parents fed on M. crassus, whereas X. ramesis from parents fed on D. dasyurus developed faster at low densities. A negative effect of density on the development of offspring from egg to imago in X. conformis was manifested mainly when parent fleas fed on D. dasyurus, whereas the negative effect of density on offspring development in X. ramesis was manifested mainly when parent fleas fed on M. crassus. Although there was no general effect of parent density on the resistance of imago offspring to starvation, male X. ramesis from parents fed at the highest density survived starvation for significantly shorter times compared with those from parents fed at lower densities. Manifestation of the negative effect of parent density on offspring quality appears to vary with flea species and may be affected by host species.

Ultimate mechanisms of age-biased flea parasitism

Mechanisms that cause nonrandom patterns of parasite distribution among host individuals may influence the population and evolutionary dynamics of both parasites and hosts, but are still poorly understood. We studied whether survival, reproduction, and behavioral responses of fleas (Xenopsylla conformis) changed with the age of their rodent hosts (Meriones crassus), experimentally disentangling two possible mechanisms: (a) differential survival and/or fitness reward of parasites due to host age, and (b) active parasite choice of a host of a particular age. To explore the first mechanism, we raised fleas on rodents of two age groups and assessed flea survival as well as the quantity and quality of their offspring. To explore the second mechanism, three groups of fleas that differed in their previous feeding experience (no experience, experience on juvenile or experience on adult rodents) were given an opportunity to choose between juvenile and adult rodents in a Y-maze. Fleas raised on juvenile rodents had higher survival and had more offspring that emerged earlier than fleas raised on adults. However, fleas did not show any innate preference for juvenile rodents, nor were they able to learn to choose them. In contrast to our predictions, based on a single previous exposure, fleas learned to choose adult rodents. The results suggest that two mechanisms-differential survival and fitness reward of fleas, and associative learning by them-affect patterns of flea distribution between juvenile and adult rodents. The former increases whereas the latter reduces flea densities on juvenile rodents. The ability of fleas to learn to choose adult but not juvenile hosts may be due to: (a) a stronger stimulus from adults, (b) a higher profitability of adults in terms of predictability and abundance, or (c) the evolutionary importance of recognizing adult but not juvenile hosts as representatives of the species.

Reproductive success in two species of desert fleas: density dependence and host effect

We tested the hypothesis that a negative fitness-density relationship exists in haematophagous ectoparasites. We studied the effect of flea density on the number of blood meals necessary for starting oviposition and egg production in Xenopsylla conformis and Xenopsylla ramesis when exploiting two rodent hosts, Meriones crassus and Gerbillus dasyurus. The number of blood meals taken by a flea prior to first oviposition was similar in both flea species but was dependent on flea density and differed significantly between hosts. When parasitizing G. dasyurus, females of both flea species required a similar number of blood meals to start oviposition, independent of density. By contrast, fleas on M. crassus at higher densities needed less blood meals than at lower densities. Egg production of female fleas differed significantly between flea and host species and was affected by flea density. X. ramesis produced more eggs than X. conformis. When parasitizing G. dasyurus, density did not affect the number of eggs produced by X. conformis, however, when on M. crassus, this flea produced significantly less eggs at the highest density. The number of eggs produced by X. ramesis at high densities was significantly lower than at low densities when it parasitized either host species. Results of this study demonstrated that reproductive success of fleas was density dependent and, in general, decreased with an increase in density. However, the effect of density on reproductive performance was manifested differently on different host species.

A search for the rodent hosts ofLeishmania majorin the Larestan region of southern Iran: demonstration of the parasite inTatera indicaandGerbillussp., by microscopy, culture and PCR

Zoonotic cutaneous leishmaniasis (CL) caused by Leishmania major occurs widely in Iran, where several species of rodent serve as the parasite's 'reservoir' hosts. In an attempt to identify the rodent hosts in the Larestan region, which lies in the Fars province of southern Iran (where the incidence of human CL has been rising), 32 rodents (20 Tatera indica, eight Meriones crassus, four Gerbillus sp.) were caught and checked for leishmanial infection. Using two detection methods (the microscopical examination of stained tissue smears and the culture of tissue samples) and a PCR to identify any leishmanial parasites detected, L. major was identified in six of the rodents caught: two male T. indica from Alamarvdasht, two female T. indica from Lamerd, and two females of the genus Gerbillus (one caught in Lamerd and one in Lar). Although the samples were too small to prove that M. crassus is not a significant host of L. major in Larestan, they were large enough to indicate that T. indica and members of the genus Gerbillus serve as reservoir hosts of L. major in the region. Tatera indica appears to be an important host of L. major across much of Iran but this appears to be the first time that the genus Gerbillus has been found to be involved in the epidemiology of CL in the country.

Density dependence of feeding success in haematophagous ectoparasites

We studied the effect of density on feeding success of 2 fleas, Xenopsylla conformis and Xenopsylla ramesis, when exploiting rodents Meriones crassus and Gerbillus dasyurus. We tested 2 alternative hypotheses: (i) that intraspecific interference competition occurs and, thus, feeding success of a flea decreases with an increase in density and (ii) that facilitation via suppression of a host defence system occurs and thus, feeding success of a flea increases with an increase in density. The mean size of a bloodmeal and the proportion of highly engorged individuals in X. conformis feeding on both hosts were affected by density. When on G. dasyurus, both the size of a bloodmeal and the proportion of highly engorged individuals were lower at low (5-15 fleas per host) than at high (25-50 fleas per host) densities. The opposite was true when this flea fed on M. crassus. The mean bloodmeal size and proportions of highly engorged X. ramesis parasitizing either host were not affected by flea density. This study showed that the density dependence of feeding success of a flea (a) varied both between fleas and within-fleas between hosts and (b) indicated either intraspecific competition or facilitation via the host in a particular flea-host association.

Benefits, Costs and Constraints of Anti‐Parasitic Grooming in Adult and Juvenile Rodents

AbstractGrooming behaviour plays various roles in the health care, reproduction, and social life of an individual vertebrate. However, the reasons for the variability in time spent grooming amongst species, populations and individuals are not fully understood. We tested the hypothesis that the main role of grooming is ectoparasite removal and thus that time spent grooming by an animal reflects the costs of parasite infestation offset against the costs of grooming. The test was conducted on a rodent,Meriones crassus, that is parasitised by a flea,Xenopsylla conformis. We monitored behaviour of juvenile and adult rodents before and after flea infestation and quantified the probability of mortality of fleas with respect to the time spent grooming in adults compared with juvenile rodents. We predicted that: (1) increased costs of flea infestation (e.g. in parasitised as opposed to flea‐free rodents and in juveniles as opposed to adults) increases time spent grooming and (2) mortality probability per flea increases with increasing time spent grooming and is higher for fleas on juveniles than for fleas on adult rodents. We were interested to discover at the expense of which activity grooming is increased. Our findings established that the major role of grooming is in flea removal, as exposure to fleas evoked grooming activity in all rodents and grooming activity explained 57–70% of the variation in flea mortality. Furthermore, we showed that the rise in grooming activity was at the expense of resting. However, we found only partial support for the predicted increase in grooming time with increasing costs of flea infestation. Flea infestation did indeed increase the time spent grooming by rodents. Nevertheless, juvenile rodents who incur higher costs of flea infestation spent less time grooming than adults and sustained similar flea densities, suggesting that these hosts are constrained by some other factors, such as feeding time.

Between-host phylogenetic distance and feeding efficiency in hematophagous ectoparasites: rodent fleas and a bat host

We hypothesized that a parasite exploits most effectively its principal host, less effectively a host that is phylogenetically close to its principal host, and least effectively a host that is phylogenetically distant from its principal host. We tested this hypothesis by quantifying the feeding efficiency of two flea species (Parapulex chephrenis and Xenopsylla ramesis) on two rodents, Acomys cahirinus, the specific host of P. chephrenis, and Meriones crassus, a preferred host of X. ramesis, and one bat, Rousettus aegyptiacus, an alien host to both flea species. In both fleas, fewer individuals succeed in feeding when offered with their nonspecific or nonpreferred rodent host to feed on compared with those allowed to feed on their preferred or specific rodent host or, surprisingly, on a bat. The proportion of P. chephrenis that fed was higher on A. cahirinus than on R. aegyptiacus. In contrast, similar proportions of X. ramesis took blood from M. crassus and R. aegyptiacus. The mass-independent size of the blood meal taken by the fleas differed significantly between species, being higher in X. ramesis than in P. chephrenis. However, each flea species took similar amounts of blood from any of the three host species. The duration of early, middle, and late digestion stages differed significantly between P. chephrenis and Xenopsylla conformis, all being shorter in the former, independent of the source of blood. Both fleas digested bat blood significantly faster than the blood of either rodent host. The time of survival after a single blood meal differed significantly between flea species, with X. ramesis surviving significantly longer than P. chephrenis, although no effect of host species on flea survival was found. In terms of the evaluation criteria that we used, we concluded that (a) the alien bat host appeared not to be inferior as a source of food to a rodent host phylogenetically close to the flea's principal host and (b) that the rarity of finding rodent fleas on bats is not related to the feeding efficiency of the fleas.

Host defence versus intraspecific competition in the regulation of infrapopulations of the flea Xenopsylla conformis on its rodent host Meriones crassus

Mechanisms that regulate parasite populations may influence the evolution of hosts and parasites, as well as the stability of host-parasite dynamics but are still poorly understood. A manipulation experiment on the grooming ability of rodent hosts (Meriones crassus) and flea (Xenopsylla conformis) densities on these hosts successfully disentangled two possible regulating mechanisms: (i) behavioural defence of the host and (ii) intraspecific competition among parasites, and revealed their importance in suppressing the feeding of fleas. Moreover, the results suggest that flea competition is direct and is not mediated by host grooming, immune response, or parasite-induced damage to the host. These mechanisms, together with interspecific competition and density-dependent parasite-induced host damage, may limit the parasite burden on an individual host and may prevent parasites from overexploiting their host population.

Immunocompetence and flea parasitism of a desert rodent

Summary Immunocompetence is the general capacity of an organism to mount an immune response against pathogens and parasites. We studied the relationship between the immunocompetence of a rodent host, Meriones crassus (Sundevall's Jird) and parasitism by the flea Xenopsylla ramesis. We hypothesized that flea parasitism affects physiological and immunological variables of the host, and that the host's level of immunocompetence affects fitness components in the flea parasite. We wanted to find out (a) the effect of flea parasitism on the haematocrit (Hct), leucocyte concentration (LC) and response to phytohaemagglutinin (PHA) of the host; (b) if and how the level of immunocompetence of the host is related to the fitness of fleas exploiting it; and (c) the relationship between the immunological and behavioural defences of the host. We measured Hct and LC and response to PHA before and after 16 days of flea infestation in Sundevall's Jird and compared these variables between jirds subjected to flea parasitism and non‐parasitized (control) animals. We evaluated egg production and hatching success in fleas exploiting hosts with different levels of immunocompetence. The effect of flea parasitism on Hct and LC of rodents was manifested by an increase in among‐host variation in the temporal changes of these variables. Response to PHA injection was significantly lower in parasitized than in control animals. Flea egg production and hatching success were not related to either LC, prior to experimental treatments, or to the PHA response of rodents. However, both of these flea fitness traits were negatively correlated with changes in LC between the 1st and the 16th days of infestation. At the end of the experiment, blood consumption of fleas was measured in jirds of both treatment groups. Fleas consumed significantly more blood when they fed on previously parasitized than on non‐parasitized animals. Among fleas that fed on previously parasitized animals, blood consumption was positively correlated with the initial LC of the hosts, and negatively correlated with differences in LC between the 1st and the 16th days of flea infestation. We found no correlation between blood consumption in fleas that fed on control animals and either immunological variable of the hosts. No trade‐off was found between behavioural and immune defences of the rodent hosts.

Determination of Meriones species (Rodentiam Gerbillinae) by RAPD-PCR

Meriones crassus, Meriones persicus, and Meriones libycus from different areas of Khorasan provinces and Yazd province were studied by use of Random Amplified DNA polymorphism (RAPD) technique. DNA samples were analyzed by use of nine primers. Genetic distance among samples varied between 0.24 and 0.78. Dendrogram designed on the base of genetic distance shows separation of these species. In this research, RAPD was used for analyzing the genetic variations among these species.

Body temperature daily rhythms of the fat jird Meriones crassus: Effects of beta and alpha adrenergic blockers

(1) The responses of body temperature ( T b) daily rhythms of short photoperiod (8L:16D) acclimated fat jirds Meriones crassus, a nocturnal xeric burrowing species, to beta (propranolol, 4.5 mg/kg) and alpha (prazosine, 1 mg/kg) adrenergic blockade were studied. (2) The results of our study show that beta blockade significantly ( p<0.01) increased T b values during the dark phase (24:00 and 06:00 h) and shifted the acrophase. (3) Alpha blockade significantly ( p<0.05) decreased T b values during the dark phase (24:00 h) but significantly ( p<0.01) also increased T b during the light phase (12:00 h). (4) These responses are similar to those obtained for two different diurnal species inhabiting arid environments and differ from those of the nocturnal golden hamster.

Immunohistochemical Localization of Distinct Angiotensin II AT1 Receptor Isoforms in the Kidneys of the Sprague‐Dawley Rat and the Desert Rodent Meriones Crassus

Employing a purified lgG fraction of a polyclonal anti-AT1 receptor anti-body, raised against a synthetic octapeptide encompassing residues 14-21 of the first extracellular domain of the AT1 polypeptide, selective AT1 receptor expression was immunohistochemically demonstrable within renal structures in Sprague-Dawley (SD) rats and the desert rodent Meriones crassus. In both animal models, prominent AT1 receptor labelling was evident in renal vascular elements, particularly cortical inter-lobular arteries (IA) as well as vasa recta bundles in the inner stripe of the outer medulla. Less intense labelling was observed among peritubular capillary endothelia within the deep cortex, and at both the outer stripe and the inter-bundle regions of the inner stripe of the outer medulla. The binding of the anti-peptide anti-body was, however, lacking among glomeruli and, except for the intense labelling confined to basement membranes of Bowman's capsule of deep nephrons, was virtually absent in all renal tubular structures of both animal models. Structural assessment of the expressed AT1 receptors by two-dimensional Western blotting revealed that a spectrum of structurally distinct AT1 receptor isoforms is expressed in the renal tissues of both animal models. This spectrum was constituted by isoforms of equal size (70 kDa) but distinct pls in SD rats, and of both different sizes (67-73 kDa) and isoelectric points in M. crassus. In either species, the charge and/or size heterogeneity of AT1 receptor isoforms may be attributed in part to differential post-translational glycosylation mechanisms of the AT1 receptor polypeptide backbone. The potential for the differential glycosylation state of AT1 receptors to alter recognition properties may add another level of complexity to tissue-specific and/or species-specific mechanisms underlying angiotensin II interactions in the kidney.

Is a starving host tastier? Reproduction in fleas parasitizing food‐limited rodents

Summary We hypothesized that food availability, and therefore body condition, of a rodent host, Meriones crassus, affects egg production and survival, and development time of preimago and adults of the first generation of the flea Xenopsylla ramesis. Egg production was significantly higher in fleas parasitizing underfed than control animals. Food availability for hosts affected survival of eggs and larvae produced by fleas on these rodents, but did not affect survival of pupae. More than twice the number of eggs from fleas on food‐limited hosts survived than those from fleas on control rodents. Highest larval survival was recorded in fleas on rodents with 30% of maintenance energy intake. Survival of new generation imagos was lowest in fleas from parents on hosts with the highest food limitation. By contrast, survival of parent fleas was highest on hosts offered 30% of maintenance energy intake. Time of egg and larval development was longest on hosts consuming 30% of energy requirements for maintenance. By contrast, there was no difference in time to emergence in pupae from flea females on rodents from different treatments. Survival time under starvation of imago of the first generation was shortest in offspring of fleas that parasitized M. crassus offered the minimal amount of food. The opposite was true for parent fleas. The results suggest nutritional and/or energetic cost of host resistance, measured as host‐mediated parasite fitness loss, as well as possible adaptive stress‐induced immunosuppression.

Sex-biased parasitism, seasonality and sexual size dimorphism in desert rodents

We investigated seasonality of gender differences in the patterns of flea infestation in nine rodent species to test if sex-biased parasitism in terms of mean abundance, species richness, prevalence and the level of aggregation (a) varies among hosts and between seasons, and (b) is linked to sexual size dimorphism. Sexual size differences were significant in both summer and winter in Acomys cahirinus, Gerbillus pyramidum and Meriones crassus, and in winter only in Acomys russatus, Gerbillus dasyurus, Gerbillus nanus and Sekeetamys calurus. Sexual size dimorphism was male biased except for A. russatus in which it was female biased. Manifestation of sexual differences in flea infestation was different among hosts between seasons. A significant effect of sex on mean flea abundance was found in six hosts, on mean flea species richness in five hosts and on prevalence in two hosts. Male-biased parasitism was found in summer in one host only and in winter in five hosts. Female-biased parasitism occurred in winter in A. russatus. Gender differences in the slopes of the regressions of log-transformed variances against log-transformed mean abundances occurred in three hosts. No relationship was found between sexual size dimorphism and any parasitological parameter in any season using both conventional regressions and the method of independent contrasts. Our results suggest that sex-biased parasitism is a complicated phenomenon that involves several different mechanisms.

Dietary intake and time budget in two desert rodents: a diurnal herbivore, Psammomys obesus, and a nocturnal granivore, Meriones crassus

We studied dietary intakes and time budgets in two desert gerbillids, Psammomys obesus, a diurnal herbivore, and Meriones crassus, a nocturnal granivore. P. obesus was offered fresh leaves of Atriplex halimus while M. crassus was offered millet seeds and Atriplex halimus, mainly as a source of water. We predicted that the (1) nocturnal rodent will feed mainly at night and the diurnal rodent mainly during the day; and (2) the herbivore consuming a relatively low energy diet will spend more time feeding than the granivore consuming a relatively high energy diet. The latter prediction was confirmed in that P. obesus spent more time feeding than M. crassus. Number of feeding sessions in M. crassus was the same as in P. obesus but each feeding session was shorter. However, the former prediction was only partially confirmed. Feeding during the dark phase was significantly longer than the light phase in the nocturnal M. crassus, as predicted; but feeding did not differ between diel phases in the diurnal P. obesus. The large amount of forage required by P. obesus necessitated consumption throughout the light and dark phases at the same rates of intake.

Larval interspecific competition in two flea species parasitic on the same rodent host

Abstract. 1. The fleas Xenopsylla conformis and Xenopsylla ramesis exploit the same rodent host, Meriones crassus, and replace each other between two different habitats situated at the opposite sides of a steep precipitation gradient. It was hypothesised that the reason for this paratopic distribution is competition between larvae of the two species for food resources.2. This hypothesis was tested by studying the performance of larvae of the two species in terms of their developmental success in mixed‐species and single‐species treatments under different air temperatures, relative humidities, substrate textures, and food abundance.3. The number of individuals of X. conformis that survived until emergence depended significantly on the presence of competing species, being, in general, lower in mixed‐species compared with single‐species treatments. The decrease in developmental success of X. conformis in mixed‐species treatments was found mainly during food shortage. In contrast, presence of the competitor did not affect the number of X. ramesis that survived until emergence. No effect of the presence of the competitor on duration of development or sex ratio was found in either species.4. The results of this study, together with the results of our previous studies, provide an explanation for the paratopic distribution of X. conformis and X. ramesis that exploit the same host species.

Fitness consequences of host selection in ectoparasites: testing reproductive patterns predicted by isodar theory in fleas parasitizing rodents

Summary Fleas Xenopsylla conformis and Xenopsylla ramesis parasitize the rodents Meriones crassus and Gerbillus dasyurus. Previously reported isodar analysis of host selection suggested that at low density, X. conformis parasitizes M. crassus only, but with an increase in flea density, G. dasyurus is also parasitized. Xenopsylla ramesis at low density parasitizes both hosts equally, whereas at high density prefers M. crassus. The ultimate cause of underlying these patterns was suggested to be differential fitness reward of parasitism on a particular host species, while the mechanism can be adaptive host selection by fleas. To justify the suggested fitness–density relations, we studied reproductive success in X. conformis and X. ramesis feeding on either M. crassus or G. dasyurus. We hypothesized that reproductive success would differ between two host species for each flea species. Xenopsylla conformis parasitizing M. crassus produced more eggs than when parasitizing G. dasyurus, whereas time of oviposition and larval hatching did not depend on host species. In contrast, egg production in X. ramesis did not differ between host species. However, fleas fed on M. crassus needed fewer bloodmeals, oviposited earlier and hatching of their larvae took less time than those of fleas fed on G. dasyurus. Patterns of egg production and development time in both fleas were consistent with the hypothesis that their between‐host distribution arose from adaptive host selection strategy.

Average daily metabolic rate, reproduction and energy allocation during lactation in the Sundevall Jird Meriones crassus

Summary Non‐reproducing Sundevall Jird (Meriones crassus) females (body mass = 84 g; n = 51), with a mean average daily metabolic rate (ADMR) of 88 kJ day−1, were divided into three groups: high (H), medium (M) and low (L) ADMR. It was hypothesized that ADMR is related to reproductive rate and predicted that the H group could support a higher reproductive rate than the L group. It was also hypothesized that allocation of energy differs with ADMR level and predicted that the H group would use mainly the reallocation of metabolizable energy to compensate for an increased energy demand for reproduction whereas the L group would increase their metabolizable energy intake markedly. To test the hypotheses, the females were mated and, in those that had litters (n = 32), changes in body mass and metabolizable energy intake were determined and milk production was estimated during 15 days of lactation. Litter size, offspring mass and growth rate were determined for pups. Body mass of dams, litter size and body mass of young at birth were similar among ADMR groups. However, milk production was 42% higher and litter mass at 15 days was significantly greater in the H than in L group, supporting our first hypothesis. All females were in negative energy balance during lactation. Mobilization of body energy reserves increased with litter size but was similar among ADMR groups. In addition, the increase in metabolizable energy intake of lactating females above that of non‐reproducing females was similar among ADMR groups and therefore the second hypothesis was rejected. ADMR was reduced by 23% during lactation and milk energy was only 30% of total metabolizable energy invested in milk production in all females. It is concluded that lactating M. crassus used a combination of reallocation of energy and increased metabolizable energy intake during lactation. The efficiency of offspring production did not differ among ADMR groups and therefore a high ADMR has an advantage when food is abundant, whereas a low ADMR has an advantage when food is sparse.

THE DIET OF THE BARN OWL TYTO ALBA IN THE NEGEV DESERT

Food remains left by predators, and pellets in particular, are a good source of information about species composition in a particular area. Such information is essential for research and conservation purposes. We report here on the composition of an assemblage of barn owl (Tyto alba) pellets collected from the Holot Agur Nature Reserve located in the sand dunes in the northwestern Negev, about 10 km north of Nizzana, at 30o58′N 34o24′E. Most of the material was in compacted form, with some in the form of whole pellets. The remains were collected on 18 November 2002 from an old bus that had been abandoned in the area years before. The climate of this area is arid, with an average annual rainfall of about 100 mm, concentrated mainly between December and February (Jaffe, 1988). In the northern Negev the average mean monthly ambient temperature ranges between 11 oC in January and 26 oC in July (Jaffe, 1988). The bus was located in sand dunes where the plant community is composed mainly of low bushes of Arthemisia monosperma and Retema roetam. The area within a radius of about 1 km from the bus is devoid of trees, caves, or other potential nesting or roosting sites suitable for barn owls. Judging by the amount of material and eggshells, the bus has apparently been used for several years by barn owls. The material was brought to the lab in Tel Aviv where it was soaked for 24 hours in water, after which the bones and exoskeletons of invertebrates were separated from vegetational material and hair. Skulls and mandibles were identified using the reference collection of the Zoological Museum of Tel Aviv University. The minimum number of individuals (MNI) per species was calculated from mandibles or crania. The assemblage was composed mostly of small mammals (97%), some reptiles, and a few bones of birds in addition to some invertebrates (Table 1). It contained the remains of at least 1026 specimens, 989 of which were mammals belonging to 10 species of rodents—seven of the family Gerbillidae, two species of shrews (the common shrew and the pygmy white-toothed shrew), and an insectivorous bat. In addition, there were chameleons, geckos, and Agama lizards. The most abundant species were gerbils— Gerbillus allenbyi, G. pyramidum, and G. gerbillus (some of which may belong to G. dasyurus, whose mandibles are indistinguishable from those of G. gerbillus)—followed by the common shrew Crocidura suaveolens and the jirds Meriones crassus and M. sacramenti. All species found were known to occur in or near the area (Yom-Tov, 1988; Werner, 1988; Mendelssohn and Yom-Tov, 1999; Yom-Tov and Dayan, 1996). NOTE: