Canine carnassials: character displacement in the wolves, jackals and foxes of Israel

Previous research implies that competitive character displacement in felids and mustelids of Israel is expressed by canine size. Anatomy and observed killing behaviour of canids suggest that canines in this group are less adapted for the stylized role they play in felids and mustelids. Thus we hypothesized that character displacement, if it exists in canids, should not be manifested more clearly by canine size than by other traits. Five sympatric and at least partially syntopic canids occupy Israel, while in North Africa the largest (wolf) and smallest (Blanford's fox) are absent. Sexual size dimorphism in Israeli canids is generally less than in felids and mustelids (in which we analysed each sex as a separate ‘morphospecies’), so we used mixed-sex samples to represent each species. The three largest species (wolf, golden jackal and red fox) are also represented by Middle Palaeolithic samples in Israel, and all three had larger carnassial lengths then. Carnassial lengths, canine diameters and skull lengths are all remarkable evenly spaced among the five recent species in Israel. In Egypt, no trait manifests significant equality. Despite regional fluctuations in size, the carnassial length ratios of the three smaller species (foxes) are strikingly constant (1.18–1.21) throughout the region, while the ratios for the three larger species (wolf, jackal and red fox), sympatric only in Israel, are larger (1.33–1.34). Finally, mean carnassial length of jackals is constant across North Africa, while skull length and canine diameter both increase from Algeria through Egypt. All three traits are larger in Egypt than in Israel. We tentatively ascribe the equal ratios in Israel to competitive character displacement, though this hypothesis is speculative because of numerous lacunae in knowledge of diet, killing behaviour, available resources and extent of food limitation. Furthermore, humans have greatly affected range, density and ecology of wolves and jackals in the last century. Larger sizes in the Palaeolithic may well be manifestations of Bergmann's rule. The constancy of carnassial length in North African jackals, notwithstanding a longitudinal cline in CBLs of these populations, and the constant ratio between jackal and red fox carnassial length are both consistent with a hypothesis of character release in the absence of the wolf.     

Genetic structure and expansion of golden jackals (Canis aureus) in the north-western distribution range (Croatia and eastern Italian Alps)

The golden jackal, widely distributed in Europe, Asia and Africa, is one of the less studied carnivores in the world and the genetic structure of the European populations is unknown. In the last century jackals strongly declined mainly due to human persecution, but recently they expanded again in eastern Europe. With the aim to determine the genetic structure and the origin of expanding jackals, we analyzed population samples obtained from Bulgaria, Serbia, Croatia (Dalmatia and Slavonia) and individuals sampled in north-eastern Italy. Samples were typed at the hypervariable part of the mitochondrial DNA control-region (mtDNA CR1) and at 15 canine autosomal microsatellite loci (STR), and analyzed using multivariate, Bayesian and landscape genetic methods. The mtDNA CR1 was monomorphic, showing a single haplotype shared among all the populations. The STR loci were variable, with 2–14 alleles and intermediate values of heterozygosity (Ho = 0.47; He = 0.51). Genetic diversity was significantly partitioned (θ_ST = 0.07; P < 0.001) and the populations were partially distinct, perhaps in consequence of recent fragmentations. Jackals from Dalmatia were the most genetically differentiated. Assignment testing and gene flow analyses suggested that jackals colonizing Italy have admixed origins from Dalmatian and Slavonian populations. They are not first generation migrants, suggesting that dispersal towards north-eastern Italy is a stepping-stone process. Golden jackal and wolf colonization patterns might be different, with prevalent short-distance dispersal in jackals versus prevalent long distance dispersal in wolves. The admixed origin of jackals in the Alps ensures abundant genetic variability, which may enhance adaptive fitness and expectancy of population growth. The intersections between Dinaric–Balkan and Eastern Alps are areas of population expansion and admixture, highlighting their conservation, ecological and evolutionary values.     

Interspecific competition and torpor in golden spiny mice: two sides of the energy-acquisition coin

We studied the occurrence of torpor in golden spiny mice in a hot rocky desert near the Dead Sea. In this rodent assemblage, a congener, the nocturnal common spiny mouse, competitively excluded the golden spiny mouse from the nocturnal part of the diel cycle and forced it into diurnal activity; this temporal partitioning allows the two species to partition their prey populations, particularly in summer when the diet of the two species is comprised mainly of arthropods, and largely overlap. We studied the effect of the presence of the common spiny mice at two resource levels (natural food availability and food added ad libitum) on populations of golden spiny mice in four large outdoor enclosures: two with common spiny mice removed and two enclosures with populations of both species. We hypothesized that with interspecific competition and/or reduced resources, golden spiny mice will increase their use of torpor. As we expected, supplemented food reduced the total time spent torpid. In summer, when the different activity periods of the two species results in prey species partitioning, removal of the congener did not affect torpor in the golden spiny mouse. However, in winter, when insect populations are low and the two species of mice overlap in a largely vegetarian diet, removal of the common spiny mouse reduced torpor in golden spiny mice, whether food was supplemented or not. This result suggests that torpor, a mechanism that allows small mammals to sustain periods of low availability of resources or high energetic requirements, may also help them to tolerate periods of enhanced interspecific competition. This may be a significant short-term mechanism that reduces competition and hence increases fitness, in particular of individuals of the subordinate species whose accessibility to resources may be limited.     

Gait choice in desert-living black-backed jackals

Gait selection is a strategy used by quadrupeds to meet the demands of locomotion under variable environmental conditions. The movement of black-backed jackals Canis mesomelas within a desert area was investigated. The usage and distribution of gaits in three distinct desert environments in the Namib Desert, Namibia, were analysed. The areas were chosen based on topographical differences: a bare, a featureless sand plain in an interdune valley, a large sand dune and a narrow dune valley with clumped plant growth. Fresh jackal tracks were recorded by GPS once a week for 1 year. Gait types, gait segment lengths and the rate of switches between gaits were analysed. Trot was the most frequently used gait in all areas, followed by walk and the two types of gallop. Jackals used faster gaits, with the lowest number of gait switches in the interdune plain. Movements on the sand dune were characterized by shorter gait segment lengths and frequent gait changes. In the dune valley, movements were slower and the rate of gait changes was intermediate between the other two areas. The strongest influence on gait choice and on gait changes was found to be the terrain topography, mainly the grade. Gait and track choice can be seen as a dynamic adaptation to a demanding environment like the Namib Desert.     

Interspecific hybrids between Romanian and Kurdistan hamsters

From crossings between Mesocricetus brandti and Mesocricetus newtoni 23 hybrids were obtained which presented characters intermediate between the parents and which were completely sterile. The number of chromosomes in the hybrid animals (2n=40) is also intermediate between the parents and the karyotype presents two distinct chromosome sets corresponding to those in the two parent species. The regular presence of multivalents at diakinesis and metaphase I probably causes the non balanced disjunction of the genetic material, and thus, probably, the total sterility of the hybrids. The study of sex chromatin showed the existence of a sex dimorphism, the female presenting more nuclei with 1–2 sex chromatin bodies. The presence of 2 sex chromatin bodies of different sixes may be explained by the heteroehromatinization of a whole X chromosome and half of its homologue.Histological study showed that the male and female genital apparatus are intensively affected in hybrids and the spermatogenetic and oogenetic activity is generally stopped. This determines the total sterility of the hybrids.     

Interspecific hybridization between greater kudu and nyala

Hybridization of wildlife species, even in the absence of introgression, is of concern due to wasted reproductive effort and a reduction in productivity. In this study we detail an accidental mating between a female nyala (Tragelaphus angasii) and a male greater kudu (T. strepsiceros). The hybrid was phenotypically nyala and was identified as such based on mitochondrial DNA. Further genetic analysis based on nine microsatellite markers, chromosome number and chromosome morphology however, confirmed its status as an F1 hybrid. Results obtained from a reproductive potential assessment indicated that this animal does not have the potential to breed successfully and can be considered as sterile.     

Aggressive howling in wolves

During two studies that investigated the responses of wolf packs to either human simulations or pre-recorded playbacks of wolf, Canis lupus, howling, single adult wolves from five different packs approached my location and howled on a total of six occasions. The howls uttered by these close-approaching wolves were significnatly deeper in pitch than comparable samples of howls recorded from animals that did not approach. In addition, howls of two of the five animals differed in structure from most of the other howls recorded during both studies. These close-approach howls were characterized by the presence of harmonically unrelated frequency sidebands near the end of the howl. This feature was rate in howls recorded during occasions when wolves kept their distance. These results indicate that the structure of wolf howling during aggressive interactions with strange wolves follows Morton's (1977) motivation-structural rules, which state that natural selection will favour the use of low-frequency, harsh sounds by hostile animals. This relationship follows from the physical constraints of vocal production: animals of larger size can produce sounds of lower pitch and harsher tonal quality. As body size is a primary determinant in the outcome of aggressive interactions, vocalizations signalling size (i.e.low-pitched, harsh sounds) will be of selective value for individuals engaged in aggressive interactions.     

Blastomycosis in wild wolves

Blastomycosis was fatal to a wild wolf in Minnesota, and serologic evidence of blastomycosis was found in a Wisconsin wolf. No unusual movements were detected in the Minnesota animal from October 1983 through October 1985. However, by early December 1985, this wolf was weak and debilitated, and it perished on 14 December after approaching a human residence.     

Interspecific combative interactions between wood-decaying basidiomycetes

Competition is the most common type of interaction occurring between wood-decaying higher fungi. Since competition for nutrients in organic resources is effectively brought about by competition for space, the common division into interference and exploitation competition is not very appropriate. Fungal competition can be divided into primary resource capture (obtaining uncolonized resources) and secondary resource capture (combat to obtain resources already colonized by other fungi). Combative mechanisms include antagonism at a distance, hyphal interference, mycoparasitism and gross mycelial contact. Interactions can result in deadlock or replacement, and a hierarchy of combative ability can be discerned amongst fungi that inhabit particular resources, but within this hierarchy there exists intransitivity, modification of outcome by other species and abiotic variables. Interactions can dramatically alter mycelial function, and have potential as biological control agents of fungal pathogens of trees and in service timber.     

Interspecific hybridisation between Candida albicans and Candida tropicalis

Abstract Protoplasts from auxotrophic mutants of Candida albicans and Candida tropicalis were produced by snail enzyme treatment and their fusion was induced with polyethylene glycol (PEG). During selective regeneration, nutritionally complemented interspecific hybrids were obtained. Their cells contained one nucleus, and the DNA content per cell was higher than in the parents. The isoenzymic and sugar assimilation patterns of the mutants, and those of the hybrids and the products after their haploidisation, were also analysed. The results indicated that the hybrids were partial alloploids containing the total chromosomal set of either of the parental species and one or a few chromosomes of the other.     

Interspecific hybrid between Allium cepa and Allium sativum

Summary Interspecific hybrids between Allium cepa and Allium sativum were obtained using the fertile clone A. sativum as the male parent. The nascent embryos which formed shortly in interspecific hybridization between A. cepa and A. sativum were rescued by ovule culture at an early stage. The zygotes or proembryos developed in Murashige and Skoog medium containing 5.7×10^-8 M indole-3-butyric acid (IBA). Once developed, the embryos were taken out of the ovule and cultured on embryo culture medium where they regenerated into whole plants. The hybridity of the plants obtained was examined by morphological observation, chromosome analysis, and ribosomal RNA gene analysis. The analyses proved that the plants were mature sexual hybrids between A. cepa and A. sativum. Each hybrid plant had keeled but fistulose leaves and formed a bulb resembling that of A. cepa. The hybrids produced not only S-propenyl-l-cysteine sulfoxide, which is the major flavor precursor in A. cepa, but also S-allyl-l-cysteine sulfoxide (alliin), which is characteristic of A. sativum.     

Inhibition training in wolves and dogs

A theoretical model previously proposed by the first author hypothesizes that dogs (C. familiaris) should perform better than wolves (C. lupus) on training tasks in which (1) cues are arbitrarily selected by the experimenter, (2) reinforcement is administered by the experimenter, and (3) the to-be-learned behavior has no perceptible, functional connection with the reinforcement. To test this hypothesis, four Eastern wolf pups (C. l. lycaon) and four Alaskan Malamute pups (C. familiaris) were administered a passive inhibition task at seven weeks of age and an active inhibition test (leash training) at 11 weeks of age. Significant differences in the predicted direction were obtained for all task variables.     

Scale-free dynamics in the movement patterns of jackals

Using conventional radio-tracking techniques employed by field ecologists, evidence for scale-free (fractal) behaviour in the foraging trajectories of a species of African jackal is presented. It is believed that the particular form of foraging strategy observed here is a response by the jackal to its need to locate resources in an unpredictable environment. The methods used in this study are completely general and can be applied to other radio-tracked species, thus beginning a systematic investigation of foraging strategies in mammals.     

Caribou, wolves and man

The migratory tundra caribou/reindeer in the Holarctic now number three million and are increasing, approaching estimated pristine quantities in North America. In contrast, the sedentary forest races south of the tree-line number about 325 000 animals, and are declining in some areas in both Eurasia and North America. The chief natural mortality factor determining the survival of neonates and adults is predation; the wolf is the major predator. Recruitment and natural adult mortality are approximately equal when wolf numbers are about 6.5 per 1000 km(2). Wolf numbers have been reduced north of the tree-line in the Nearctic since the 1970s due to hunting facilitated by snowmobile transportation. But south of the tree-line wolf numbers may be locally high (>8 per 1000 km(2)) where moose have expanded their range in this century. Caribou can adapt to economic development in the Arctic if their space for mobility to cope with their predators is kept inviolate. It should be possible, through management of wolf numbers, to increase further the abundance of caribou and wolves and provide surpluses of both species for northern peoples, yet maintain a viable large mammal ecosystem in the Arctic.