Perinatal behavior of a wild Grevy’s zebra (Equus grevyi) mare and foal

This paper describes the postpartum behavior of a wild Grevy’s zebra (Equus grevyi) mare and foal. The foal first attempted to stand within 5 min of birth and succeeded at approximately 10 min after birth. Within 40 min of birth, the infant could walk steadily. The foal did not suckle during the observation time. An ethogram of observed behaviors is provided.     

Male infanticide in captive plains zebra, Equus burchelli

On the assumption that infanticide exists in plains zebra, as reported for horses, Equus caballus, we tested the following hypothesis. Introducing a new zebra male into a herd of breeding females should increase foal mortality in comparison with herds in which the sire of the foals is still present. The younger the foal, the more likely infanticide should be. We collected data from five herds in two zoological gardens in the Czech Republic. We found nine records of infanticide in plains zebra and three cases of abortions that were probably induced by forced copulation. We analysed additional indirect data to investigate the possibility of introduced males causing other abortions. Abortions were three times more likely in herds with introduced males than with only fathers present. Postnatal mortality of the foals was four times greater with introduced males than with fathers. No indication of a sex preference was observed for infanticide by a new male for either abortions or postpartum deaths. When we combined all records involving introduced males, the probability of foal death was greatest when the new male joined the herd just after conception and decreased with increasing time between conception and date of the new male introduction (the chance of a foal surviving was less than 5% just after conception and more than 50% at the time of delivery). Mortality of foals did not depend on whether the new male was introduced before or after the foal was born. Survival increased to more than 60% after the foal reached 1 month of age. Our results suggest that captive plains zebra show the highest occurrence of infanticide reported among ungulates. Copyright 2000 The Association for the Study of Animal Behaviour.     

半散放条件下普通斑马的种群特征

<正>普通斑马又称平原斑马(Equus burchelli),隶属于奇蹄目马科,是一种极具观赏价值的大型哺乳动物。广泛分布于非洲,喜欢栖息在平原和草原,随季节和食物迁徙。普通斑马是社会性动物,习惯群体生活,规模较小的群体由1只雄性和2-6只雌性以及它们未成年的子女组成;或是由十几只未成年的雄性普通斑马组成;较大的群体则有几百只,它们通常是由若干个小规模的群体组成。雄性     

Sex preferences in Jeju pony foals (Equus caballus) for mutual grooming and play-fighting behaviors

We investigated mutual grooming by Jeju pony (Equus caballus) foals to determine whether male foals preferentially interact with potential future sexual partners or competitors. We predicted that relative to female foals, male foals would exchange grooming more frequently with young mares and that in general, foals would mutually groom more frequently with the opposite sex rather than the same sex. Observing 53 foals between April and October 1998, we recorded 113 mutual grooming events. Male foals exchanged grooming with yearling mares more frequently than with their mother, while female foals exchanged grooming with their mother more frequently than with yearling mares. Contrary to the prediction, foals were not more likely to mutually groom with a foal of the opposite sex than with a foal of the same sex. In our study, 21 instances of play-fighting behavior followed mutual grooming between peers. Relative to intersexual grooming events, play-fighting was more likely to follow intrasexual mutual grooming, and male foals were much more likely to play fight than female foals. These results provide evidence that Jeju pony foals develop and maintain social relationships at the earliest stage of their lives. We suggest that early social experiences might influence social bonding later when the male foal begins to form a harem after separation from its mother.     

A case of adoption and allonursing in captive plains zebra (Equus burchellii)

Although allonursing (allowing non-filial offspring to suckle) can be a costly behaviour, it has been reported for many mammals including ungulate species. However, such behaviour is very rare in equids. This is the first report on adoption and allonursing in captive plains zebra (Equus burchellii), recorded in the Dv?r Králové Zoo, Czech Republic. We observed a case of adoption of an orphaned foal by a lactating mare, who then regularly nursed two foals (filial and non-filial). The allonursing mare rejected more suckling attempts, terminated suckling bouts more often, and had a shorter suckling bout duration than other mares. When nursing both foals at the same time, the suckling bout lasted for less time than when nursing a single foal, regardless of whether it was filial or non-filial. The allonursing mare apparently did not discriminate between the filial and non-filial foal.     

Patent urachus with subsequent joint infection in a free-living Grevy's zebra foal

A free-living, female Grevy's zebra (Equus grevyi) foal was found lethargic, lame, with swollen joints, pyrexia, and urine dripping from the umbilicus. It died 2 days later despite intensive care. Gross examination revealed patent urachus and suppurative arthritis. Swabs were taken from the joints, the patent urachus, and urine for bacteriology. The dominant isolate was Escherichia coli. The joint infection was probably secondary to septicemia, resulting from the patent urachus. To our knowledge, this is the first report of neonatal patent urachus in a wild equid.     

Neurophysiological response selectivity for conspecific songs over synthetic sounds in the auditory forebrain of non-singing female songbirds

Female choice plays a critical role in the evolution of male acoustic displays. Yet there is limited information on the neurophysiological basis of female songbirds’ auditory recognition systems. To understand the neural mechanisms of how non-singing female songbirds perceive behaviorally relevant vocalizations, we recorded responses of single neurons to acoustic stimuli in two auditory forebrain regions, the caudal lateral mesopallium (CLM) and Field L, in anesthetized adult female zebra finches (Taeniopygia guttata). Using various metrics of response selectivity, we found consistently higher response strengths for unfamiliar conspecific songs compared to tone pips and white noise in Field L but not in CLM. We also found that neurons in the left auditory forebrain had lower response strengths to synthetics sounds, leading to overall higher neural selectivity for song in neurons of the left hemisphere. This laterality effect is consistent with previously published behavioral data in zebra finches. Overall, our results from Field L are in parallel and from CLM are in contrast with the patterns of response selectivity reported for conspecific songs over synthetic sounds in male zebra finches, suggesting some degree of sexual dimorphism of auditory perception mechanisms in songbirds.     

Tracing the development of learned song preferences in the female zebra finch brain with functional magnetic resonance imaging

In sexually dimorphic zebra finches (Taeniopygia guttata), only males learn to sing their father's song, whereas females learn to recognize the songs of their father or mate but cannot sing themselves. Memory of learned songs is behaviorally expressed in females by preferring familiar songs over unfamiliar ones. Auditory association regions such as the caudomedial mesopallium (CMM; or caudal mesopallium) have been shown to be key nodes in a network that supports preferences for learned songs in adult females. However, much less is known about how song preferences develop during the sensitive period of learning in juvenile female zebra finches. In this study, we used blood-oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to trace the development of a memory-based preference for the father's song in female zebra finches. Using BOLD fMRI, we found that only in adult female zebra finches with a preference for learned song over novel conspecific song, neural selectivity for the father's song was localized in the thalamus (dorsolateral nucleus of the medial thalamus; part of the anterior forebrain pathway, AFP) and in CMM. These brain regions also showed a selective response in juvenile female zebra finches, although activation was less prominent. These data reveal that neural responses in CMM, and perhaps also in the AFP, are shaped during development to support behavioral preferences for learned songs.     

Localization of androgen receptor mRNA-containing cells in avian respiratory-vocal nuclei: An in situ hybridization study

Song development and song pattern formation in oscine songbirds are influenced by steroid hormones such as estrogens and androgens, and the control of vocal pattern generation is mediated via a network of interconnected vocal and respiratory nuclei. The main components of the respiratory part of the network are the expiratory and inspiratory premotor nuclei, known as retroambigualis (RAm) and the rostral ventral respiratory group (rVRG), respectively. These respiratory components play an integral role in song production either by providing the expiratory pulses of air required for each and every song syllable, or by controlling inspiration between syllables in the form of minibreaths, and between phrases for major replenishments of air. Here we analyze the distribution of androgen receptors (AR) and estrogen receptors (ER) in the midbrain and hindbrain of male and female zebra finches, and male canaries and green finches, using in situ hybridization with cRNA probes of the zebra finch AR and ER. ERmRNA was not expressed in any of the respiratory-vocal nuclei of the midbrain or hindbrain, but ARmRNA was expressed in the tracheosyringeal motor nucleus (nXIIts) and in RAm and rVRG. The size of the ARmRNA defined RAm and rVRG was similar in male and female zebra finches, but the size of ARmRNA defined nXIIts was slightly sexual dimorphic. Previously undescribed areas of ARmRNA expression outside the respiratory-vocal network in the brain stem were the nucleus semilunaris and layers 10–12 of the optic tectum. ARmRNA expression in the respiratory-vocal nuclei of adult male songbirds, adult female zebra finches, and juvenile zebra finches suggests that the temporal pattern of learned and unlearned vocalizations is sensitive to androgen-dependent mechanisms mediated by RAm and rVRG. © 1997 John Wiley & Sons, Inc. J Neurobiol 33: 865–876, 1997     

Cape mountain zebra in the Baviaanskloof Nature Reserve,South Africa: resource use reveals limitations to zebra performance in a dystrophic mountainous ecosystem

Resource use of Cape mountain zebra was studied in the Baviaanskloof Nature Reserve (BNR) over concerns of the poor performance in population growth. We assessed the seasonal diet, habitat suitability and forage quality of the Bergplaas area in BNR for mountain zebra. Grasses contributed 95.2% to the annual diet of mountain zebra, Tristachya leucothrix contributing the most (39.4%), followed by Themeda triandra (27.6%). Seasonally, T. triandra contributed most to the diet in winter, while T. leucothrix became more important in the summer and also was the only species preferred in all seasons. Mountain zebra concentrated their feeding in Kouga Grassy Fynbos and from our assessment this was the only habitat suitable for mountain zebra. Our analysis of mountain zebra dung indicated that the seasonal nitrogen and phosphorus content was below the threshold values prescribed for grazers, and our study suggests that mountain zebra at Bergplaas are severely resource limited. We emphasize the importance of fire and access to nutrient‐rich lowlands in influencing the nutritional ecology of mountain zebra and provide conservation management recommendations.     

Spatial and behavioural measures of social discrimination by captive male zebra finches: Implications of sexual and species differences for recognition research

All bird species reproduce sexually and individuals need to correctly identify conspecifics for successful breeding. Captive zebra finches are a model system for studying the factors involved in species recognition and mate choice. However, male zebra finches’ behavioural responses in a spatial preference paradigm to a range of estrildid finch species, other than domesticated Bengalese finches, remain unknown. We investigated spatial and display responses of male zebra finch subjects to stimulus females between conspecific and four phylogeographically relevant finch species, in addition to female Bengalese finches. Surprisingly, male subjects did not show consistent spatial association with conspecific over heterospecific females. Overall, as predicted by sexual selection theory, the spatial proximity responses of males were less discriminatory compared to female zebra finches’ responses tested previously using the same paradigm. However, male subjects showed consistently more behavioural displays towards female conspecifics than heterospecifics which were positively related to the behavioural display rates of the respective female stimuli. Some male behavioural responses, other than song, also showed significant differences between the different stimulus species and consistently differed across individual test subjects, with the most individual subject variation seen in choice trials between female conspecific and Bengalese finch stimuli. The results are important for the design and interpretation of future behavioural and neurobiological experiments on species recognition systems using the zebra finch as a model species.     

Successful transfer of the embryos of Przewalski's horses (Equus przewalskii) and Grant's zebra (E. burchelli) to domestic mares (E. caballus)

Blastocysts were collected non-surgically from 2 Przewalski's horse and 2 Grant's zebra mares and transferred extra-specifically to domestic horse and donkey recipients. Nine Przewalski's horse embryos were transferred surgically, and 2 non-surgically, to domestic Welsh-type pony mares. After surgical transfer, 7 (77.8%) pregnancies were established and 4 foals were born. Twelve Grant's zebra embryos were transferred surgically to 5 pony and 7 domestic donkey recipients respectively and 1 non-surgically to a donkey; 3 (60%) zebra-in-horse pregnancies were established and 2 went to term. Only 2 (28.6%) zebra-in-donkey pregnancies were established but neither went to term, although one zebra foal was aborted alive at Day 292 but failed to survive. No pregnancies resulted from the non-surgical transfers. Measurement of chorionic gonadotrophin concentrations and parental-specific lymphocytotoxic antibodies in the serum of the recipient animals indicated a pronounced maternal immunological response to the extra-specific embryo, but this could not be correlated with success or failure of pregnancy. The results indicate that extra-specific embryo transfer may be a useful aid to breeding exotic equids in captivity.     

Molecular cloning and characterization of the germline-restricted chromosome sequence in the zebra finch

The zebra finch (Taeniopygia guttata) germline-restricted chromosome (GRC) is the largest chromosome and has a unique system of transmission in germ cells. In the male, the GRC exists as a single heterochromatic chromosome in the germline and is eliminated from nuclei in late spermatogenesis. In the female, the GRC is bivalent and euchromatic and experiences recombination. These characteristics suggest a female-specific or female-beneficial function of the GRC. To shed light on the function of GRC, we cloned a portion of the GRC using random amplified polymorphic DNA–polymerase chain reaction and analyzed it using molecular genetic and cytogenetic methods. The GRC clone hybridized strongly to testis but not blood DNA in genomic Southern blots. In fluorescent in situ hybridization analysis on meiotic chromosomes from synaptonemal complex spreads, the probe showed hybridization across a large area of the GRC, suggesting that it contains repetitive sequences. We isolated a sequence homologous to the GRC from zebra finch chromosome 3 and a region of chicken chromosome 1 that is homologous to zebra finch chromosome 3; the phylogenetic analysis of these three sequences suggested that the GRC sequence and the zebra finch chromosome 3 sequence are most closely related. Thus, the GRC sequences likely originated from autosomal DNA and have evolved after the galliform–passeriform split. The present study provides a foundation for further study of the intriguing GRC.     

Zebra mussels affect benthic predator foraging success and habitat choice on soft sediments

The introduction of zebra mussels (Dreissena spp.) to North America has resulted in dramatic changes to the complexity of benthic habitats. Changes in habitat complexity may have profound effects on predator-prey interactions in aquatic communities. Increased habitat complexity may affect prey and predator dynamics by reducing encounter rates and foraging success. Zebra mussels form thick contiguous colonies on both hard and soft substrates. While the colonization of substrata by zebra mussels has generally resulted in an increase in both the abundance and diversity of benthic invertebrate communities, it is not well known how these changes affect the foraging efficiencies of predators that prey on benthic invertebrates. We examined the effect of zebra mussels on the foraging success of four benthic predators with diverse prey-detection modalities that commonly forage in soft substrates: slimy sculpin (Cottus cognatus), brown bullhead (Ameirus nebulosus), log perch (Percina caprodes), and crayfish (Orconectes propinquus). We conducted laboratory experiments to assess the impact of zebra mussels on the foraging success of predators using a variety of prey species. We also examined habitat use by each predator over different time periods. Zebra mussel colonization of soft sediments significantly reduced the foraging efficiencies of all predators. However, the effect was dependent upon prey type. All four predators spent more time in zebra mussel habitat than in either gravel or bare sand. The overall effect of zebra mussels on benthic-feeding fishes is likely to involve a trade-off between the advantages of increased density of some prey types balanced against the reduction in foraging success resulting from potential refugia offered in the complex habitat created by zebra mussels.     

Parentage verification of a mountain zebra (Equus zebra hartmannae) using polymorphic microsatellite markers

The Hartmann's mountain zebra (Equus zebra hartmannae) has been classified by the IUCN as a vulnerable species. Approximately 300 individuals, maintained in zoos throughout Europe and the United States of America, are being managed as part of a captive breeding program. An International Studbook is maintained for the Hartmann's mountain zebra at Marwell Zoological Park, UK. Despite the use of a variety of means to identify each individual in a captive herd, confusion sometimes occurs, resulting in the misidentification of an animal. Here we report the first application of DNA typing, using polymorphic microsatellite loci, to resolve a misidentification involving two female Hartmann's mountain zebra. This case demonstrates the way in which genetic tests derived from a related domesticated species may be used as an effective tool for captive management. Further, this case highlights the need to be able to conclusively identify captive individuals and to maintain accurate pedigree information for successful captive management. © 1995 Wiley-Liss, Inc.     

Demography of plains zebras (Equus quagga) under heavy predation

In natural ecosystems, ungulate densities show strong temporal variations. The ecological processes driving these fluctuations are complex: food limitation and predation are both important and can interact. Survival rates are central to this debate, but data are sparse for tropical ecosystems. Here, we estimate age- and sex-specific survival rates for plains zebra in Hwange National Park, a nutrient-poor savanna with a high predator–prey ratio. We estimated survival from a detailed Capture-Mark-Recapture (CMR) monitoring based on 248 individual life histories, for the first time in an African grazer. We controlled for variations in detection probabilities among adult females, which resulted from their social structure. As expected, annual survival was low during the first year (0.441); increased in yearlings (0.560) and peaked at 0.795 and 0.847 in adult males and females respectively. The survival of adult females was lower during the dry season, which probably resulted from higher predation due to predictable movements of zebras to waterholes. Survival at all ages was low compared to ungulates without predators. The demographic model we constructed showed a declining trend (λ = 0.94), which was consistent with the data from road counts ( = 0.92). Life Table Response Experiment (LTRE) analyses using the Serengeti and Kruger populations as references showed that the main cause of this declining trend in the Hwange population was low survival in yearling and adult females; low foal survival also contributed. In this ecosystem, predation is likely to be the main ecological process causing low survival, and therefore a decline in the zebra population.     

The zebra mussel (<Emphasis Type="Italic">Dreissena polymorpha</Emphasis>) impacts European bitterling (<Emphasis Type="Italic">Rhodeus amarus</Emphasis>) load in a host freshwater mussel (<Emphasis Type="Italic">Unio pictorum</Emphasis>)

The European bitterling, Rhodeus amarus, is a non-indigenous fish species in British fresh waters. It lays its eggs in unionid mussels which themselves are vulnerable to fouling by the non-indigenous zebra mussel, Dreissena polymorpha. Observations from an unmanipulated natural system showed that only 27% of zebra mussel-fouled Unio pictorum hosted bitterling, while 47% of unfouled U. pictorum hosted bitterling. We conducted a field experiment in the River Great Ouse catchment, Cambridgeshire, England in May–June 2007 and 2008 to quantify the impact of zebra mussels on bitterling load in host mussels. Zebra mussel-fouled unionids were significantly less likely to host bitterling than unfouled unionids. The number of unionids hosting bitterling did not differ significantly whether the zebra mussels fouling the unionid were alive or dead. Bitterling appeared to discriminate against zebra mussel-fouled unionids less as the 2007 breeding season advanced, potentially because preferred unfouled unionids had a higher bitterling load, and were therefore relatively lower quality hosts than at the start of the breeding season.     

Karyotypic polymorphism of the zebra finch Z chromosome

We describe a karyotypic polymorphism on the zebra finch Z chromosome. This polymorphism was discovered because of a difference in the position of the centromere and because it occurs at varying frequencies in domesticated colonies in the USA and Germany and among two zebra finch subspecies. Using DNA fluorescent in situ hybridization to map specific Z genes and measurements of DNA replication, we show that this polymorphism is the result of a large pericentric inversion involving the majority of the chromosome. We sequenced a likely breakpoint for the inversion and found many repetitive sequences. Around the breakpoint, there are numerous repetitive sequences and several copies of PAK3 (p21-activated kinase 3)-related sequences (PAK3Z) which showed testes-specific expression by RT-PCR. Our findings further suggest that the sequenced genome of the zebra finch may be derived from a male heterozygote for the Z chromosome polymorphism. This finding, in combination with regional differences in the frequency of the polymorphism, has important consequences for future studies using zebra finches.     

Acoustic characteristics, early experience, and endocrine status interact to modulate female zebra finches' behavioral responses to songs

Female songbirds use male songs as an important criterion for mate selection. Properties of male songs are thought to indicate the male's quality as a potential mate. Song preferences in female zebra finches are known to be influenced by two factors--early auditory experience and the acoustic characteristics of males' songs. Studies often investigate song preferences by priming females with estrogen. However, estrogenic influences on song preferences have not been studied. We investigated the relative influence of early auditory experience, acoustic features of songs, and estrogen availability on song responsiveness in female zebra finches. Juvenile female zebra finches were tutored for 10 days with 40 songs per day with one of three acoustically different song types--simple songs, long-bout songs or complex songs. A fourth group of females was untutored. Aside from this brief song exposure, females were raised and maintained without exposure to male songs. During adulthood, females' behavioral responses to the three song types were tested under three hormone conditions--untreated, estradiol-treated and 1,4,6-androstatriene-3,17-dione (ATD)-treated (to lower endogenous estrogen). Based on the results of our study, four conclusions can be drawn. First, song responsiveness in female zebra finches is strongly affected by minimal early acoustic experience. Second, inexperienced female zebra finches are inherently biased to respond more to complex songs over other song types Third, although female zebra finches are inherently biased to respond more to complex songs, early acoustic experience may either reinforce or weaken this inherent responsiveness to complex songs. Fourth, estrogen selectively accentuates song responsiveness in acoustically-experienced female zebra finches.     

An indirect effect of biological invasions: the effect of zebra mussel fouling on parasitisation of unionid mussels by bitterling fish

Invasive species represent a major threat with both direct and indirect effects on natural ecosystems, including effects on established and coevolved relationships. In a series of experiments, we examined how the interaction between two native species, a unionid mussel (Unio pictorum) and the European bitterling (Rhodeus amarus), a fish that parasitises unionids, was affected by the non-native zebra mussel (Dreissena polymorpha). The zebra mussel fouls hard substrates, including shells of living unionids, and its presence is often associated with a decrease in population density of native unionid mussels. Bitterling lay their eggs into live unionids and the embryos develop inside their gills. Using a range of zebra mussel densities, we demonstrated that zebra mussel fouling had a negative effect on the number of bitterling eggs inside the mussel host, with abundances of 5–10 zebra mussels (shell size 15–25 mm) per unionid critical for bitterling ability to utilise the host. In a further experiment, we found that bitterling did not discriminate between unfouled unionids and those fouled with five zebra mussels. Most ovipositions into fouled hosts, however, were unsuccessful as eggs failed to reach the unionid gills. We discuss implications of such unsuccessful ovipositions for bitterling recruitment and population dynamics.