The development of the reproductive organs of the male giraffe, Giraffa camelopardalis

The reproductive organs of the male giraffe differ little in morphology and histology from those of other ungulates. There is some indication that gonadal hypertrophy occurs in late fetal life. Spermatogenesis begins at 3-4 years of age and coincides with a rapid increase of testicular weight and seminiferous tubule diameter. In the fetal testis the main hormone is androsteredione (2.73 microgram/g) but in adult testes testosterone is predominant (less than 10.08 microgram/g) and delta' testosterone may also be present.     

Subendothelial fibrillar laminae in the carotid arteries of the giraffe (Giraffa camelopardalis)

Summary The endothelium in the carotid arteries of the giraffe lies on an extensive basement membrane complex that has a distinctly fibrillar component. Small electron-dense areas occur in the basal portion of the endothelium and normally in apposition to the fibrillar laminae of the basement membrane. These zones are believed here to constitute hemi-desmosomes where endothelial attachment may be most tenacious.     

Spatial ecology and habitat use of giraffe (Giraffa camelopardalis) in South Africa

The lack of long-term studies remains a limiting factor in understanding the home range, spatial ecology and movement of giraffes. We equipped eight giraffes with GPS satellite units and VHF capacity, which were built in to the collars for the remote collection of data on their movements and home ranges over two years on Khamab Kalahari Nature Reserve (KKNR) within the Kalahari region of South Africa. Giraffe numbers in KKNR dropped from 135 individuals to 111 in just five years, revealing the lack of knowledge about their required habitat needs, space use and diet. With over 1000 km² available for roaming within the reserve, habitat selection, principle and preferred food species played a significant role in home range size and overlap between individuals. These giraffes used an average annual home range of 206 km² (20 602 ha) as calculated by a 95% minimum convex polygon (MCP) with a standard deviation core home range calculated by a 50% MCP of 10.1 km² to satisfy their annual needs for survival and reproduction in their preferred vegetation. In the wet, hot season (summer: December–February) when food was abundant, giraffes frequented smaller areas (average 177 km²), while in the dry, cool season (winter: June to August) the mean home range size increased to approximately 245 km². Rainfall influenced spatial distribution since it determined vegetation productivity and leaf phenology. The different seasons influenced giraffe movements, while different vegetation types and season influenced their home range size. Season and food availability also influenced home range overlap between different giraffe herds. Home range overlap occurred when giraffes were forced to roam in overlapping areas during the dryer months when the winter deciduous nature of the majority of the tree species resulted in lower food availability. In winter, the overlap was approximately 31% and in autumn approximately 23%. During the wet and warmer months, overlapping was 15% in summer and 19% in spring, respectively. The percentage of time spent in different vegetation type areas was influenced by the abundance of the principal food species of that plant community. It is thus concluded that the movements of giraffes were primarily influenced by a combination of environmental factors such as season, rainfall and vegetation density.     

Female reproductive signaling, and male mating behavior, in the olive baboon

Baboon sexual swellings are among the largest and most colorful signals displayed by any mammal, and many baboon studies have shown an association between sexual swellings and both female and male sexual behavior. However, the extent to which female behavior and sexual swellings combine to signal the timing of ovulation and the fertile period to males, and the extent to which males use these and other signals when determining patterns of mating behavior, remain key topics of research. Here we assess the social and sexual behavior of both female and male olive baboons with respect to detailed measures of swelling size made from digital photographs, measures of fecal progestogen and estrogen levels, and estimates of the timing of ovulation and the fertile period based on those levels. Female aggression and grooming behavior were unrelated to fecal progestogen and estrogen levels, but there were some significant relationships between these hormonal measures and presenting behaviors. Measures of female behavior collected during the study did not appear to reveal the timing of ovulation or the fertile period. Male consortship behavior was closely tied to fine-scale changes in sexual swelling size, but copulation behavior was not. Copulation behavior of consorting males was, however, linked to the timing of both ovulation and the fertile period, suggesting that males did have knowledge about these timings. Together these results suggest that males used fine-scale swelling size changes when deciding when to consort, but that consorting males did not use fine-scale swelling size changes in deciding when to copulate. We propose that swelling size may advertise the period during which males should consort with females, with other signals available only from closer inspection then used by consorting males to assess the timing of the fertile period more accurately. An important implication of this interpretation is that different males may have access to different signals of ovulation at any one time. Such a system would allow females to offer different males different information simultaneously, perhaps offering a solution to the ‘female dilemma’ of how females can simultaneously assure and confuse paternity in multi-male societies.     

Assessment of contrafreeloading preferences in giraffe (Giraffa camelopardalis)

Contrafreeloading is an intriguing phenomenon in which animals will work to obtain resources, such as food, when the same resource is simultaneously freely available. Multiple hypotheses exist for why animals might choose to contrafreeload. In this study, we assessed preferences for contrafreeloading in giraffe at the Bronx Zoo to determine whether they actually preferred to contrafreeload or were simply demonstrating a willingness to contrafreeload. Food was presented in a range of distributions between an easily accessed feeding device and a more challenging one and the giraffes’ feeding behavior at these two types of feeding devices was recorded. As the experiments progressed, more giraffe used these more challenging feeders. There was significant individual variation in the expression of preference for contrafreeloading and willingness to contrafreeload. Individual, phase of the experiment, and an interaction between these factors were significant predictors of challenge feeder use. Three foraging strategies emerged among the giraffe that we termed “freeloaders,” “contrafreeloaders,” and “opportunists.” The results of this study demonstrate that multiple indices of preference are necessary when assessing contrafreeloading behavior, and that giraffe are affected to different degrees by the factors that stimulate contrafreeloading. These results may shed light on why different individuals use complex feeding enrichment devices to varying extents.     

Dentition and age determination of the giraffe Giraffa camelopardalis

Thirteen tooth eruption stages and their corresponding chronological ages are descri bed from a series of giraffe jaws. These can be used for age determination in giraffes with immature dentition. Significant correlations of the lingual crown height ( r =0-957; P < 0001) and lingual occlusal surface width ( r =0-959; P < 0001) with the number of dark staining incremental lines in the cementum of thin decalcified sections of the maxillary first molar were found. The regression equations derived from these relationships provide a further method for determining the age of a giraffe. A composite plate showing maxillary first molar wear patterns provides a means of roughly assigning an age to a particular specimen. Thin sections of undecalcified teeth, mandible measurements, various other indices of tooth wear and eye lens mass were investigated and found unsuitable for age determination in this     

Structural evidence for insertion of collagen fibres to smooth muscle cells in the carotid arterial system of the giraffe (Giraffa camelopardalis)

Summary Previous anatomical studies have failed to resolve the question relating to whether or not collagen fibres, like elastic fibres, are attached to smooth muscle cells in the arterial wall. The current ultrastructural study demonstrates the insertion of collagen fibres to the sarcolemmal dark areas in the smooth muscle cells of the carotid arterial system of the giraffe. It is concluded, therefore, that this morphological linkage between collagen and smooth muscle cells may facilitate transmission of the force of contraction between the cells and to the surrounding connective tissue framework since the myofilaments appear to be spatially placed in series with the extracellular collagen fibres at the sarcolemmal dark areas.Presented as part of Ph.D. thesis to the University of Nairobi     

Genetic structure of two populations of the Namibian giraffe,Giraffa camelopardalis angolensis

Two geographically distinct populations of giraffe (Giraffa camelopardalis) were sampled for this study, the northern Namib Desert and Etosha National Park. Population genetic parameters and relationships within subpopulations were estimated to better understand the genetic architecture of this isolated subspecies. Gene flow between the geographically separated populations can be attributed to recent translocation of giraffe between the two populations. Inbreeding estimates in the six subpopulations studied were low though we found evidence that genetic drift may be affecting the genetic diversity of the isolated populations in northern Namibia. Population dynamics of the sampling locations was inferred with relationship coefficient analyses. Recent molecular systematics of the Namibian giraffe populations indicates that they are distinct from the subspecies Giraffa camelopardalis giraffa and classified as G. c. angolensis. Based on genetic analyses, these giraffe populations of northern Namibia, the desert‐dwelling giraffe and those protected in Etosha National Park, are a distinct subspecies from that previously assumed; thus we add data on G. c. angolensis to our scientific knowledge of this giraffe of southern Africa.     

The composition and function of all‐male herds of Thornicroft's giraffe,Giraffa camelopardalis thornicrofti,in Zambia

Temporary all‐male social groups are formed in a number of animal species. We examined 34 years of data collected from 36 male Thornicroft's giraffe in the Luangwa Valley, Zambia, to test a set of predictions related to five possible functions of all‐male herds (predator protection, practicing aggressive skills, prolonging life, nutritional demands and resource learning). We found that all‐male herds were significantly smaller than mixed‐sex herds, usually contained a mature bull, and were not dependent upon season or habitat. Dyadic associations between males in single sex herds were quite weak, with <25% of potential male dyads sighted together in an all‐male herd. Our data are best explained as a resource learning strategy adopted by males to obtain more extensive knowledge about the habitat, including both food and female distribution. However, other benefits in the form of predator protection, dietary intake and sharpening competitive skills for future contests over estrous females also seem to mediate formation of giraffe all‐male groups. We conclude that the primary advantage of roaming in all‐male herds changes during the life history of males.     

Scaling of the appendicular skeleton of the giraffe (Giraffa camelopardalis)

Giraffes have remarkably long and slender limb bones, but it is unknown how they grow with regard to body mass, sex, and neck length. In this study, we measured the length, mediolateral (ML) diameter, craniocaudal (CC) diameter and circumference of the humerus, radius, metacarpus, femur, tibia, and metatarsus in 10 fetuses, 21 females, and 23 males of known body masses. Allometric exponents were determined and compared. We found the average bone length increased from 340 ± 50 mm at birth to 700 ± 120 mm at maturity, while average diameters increased from 30 ± 3 to 70 ± 11 mm. Fetal bones increased with positive allometry in length (relative to body mass) and in diameter (relative to body mass and length). In postnatal giraffes bone lengths and diameters increased iso‐ or negatively allometric relative to increases in body mass, except for the humerus CC diameter which increased with positive allometry. Humerus circumference also increased with positive allometry, that of the radius and tibia isometrically and the femur and metapodials with negative allometry. Relative to increases in bone length, both the humerus and femur widened with positive allometry. In the distal limb bones, ML diameters increased isometrically (radius, metacarpus) or positively allometric (tibia, metatarsus) while the corresponding CC widths increased with negative allometry and isometrically, respectively. Except for the humerus and femur, exponents were not significantly different between corresponding front and hind limb segments. We concluded that the patterns of bone growth in males and females are identical. In fetuses, the growth of the appendicular skeleton is faster than it is after birth which is a pattern opposite to that reported for the neck. Allometric exponents seemed unremarkable compared to the few species described previously, and pointed to the importance of neck elongation rather than leg elongation during evolution. Nevertheless, the front limb bones and especially the humerus may show adaptation to behaviors such as drinking posture. J. Morphol. 276:503–516, 2015. © 2014 Wiley Periodicals, Inc.     

A note on foetal growth and development of the giraffe Giraffa camelopardalis giraffa

The growth of the foetus of the southern giraffe is discussed. Gestation period is calculated as 457 days being the mean of 48 observations of other workers. Birthmass is taken as 102 kg from measurements on wild giraffe. This is almost twice as great as some published figures for captive giraffe. However, subspecies also differ. Foetal growth followed a typical "J" shaped curve when plotted from the mass of 24 foetuses. The increase in vertebral column length followed a straight line. Crown/rump measurements could not always be accurately taken.     

Sonomorphology of the reproductive tract in male and pregnant and non-pregnant female Rothschild's giraffes (Giraffa camelopardalis rotschildi)

The application of real-time-B-mode ultrasonography to wild and zoo animal medicine has been shown to improve the understanding of reproductive physiology in many species. Ultrasound technology is especially helpful for monitoring urogenital health, which in turn has advantages for giraffe breeding and welfare in captivity.This study aimed to ultrasonographically describe the genital organs of reproductively healthy male and female giraffes. Through the use of a restrainer, repeated rectal ultrasound examinations were performed over a 2 year period in 2.6 Rothschild's giraffes. Changes in ovarian activity were monitored throughout four different reproductive stages in the females and included immature, mature-cycling, pregnancy, post-partum-period. In the immature giraffes the ovaries showed multiple follicles of which larger ones luteinized to form pseudo-corpora lutea. By comparison, in the mature giraffes the dominant follicle reached an ovulatory diameter of 18.5 ± 0.89 mm. After ovulation, a single corpus luteum rapidly formed and reached a maximum diameter of 33.0 ± 2.4 mm on average. Pregnancy was detected for the first time by the embryonic vesicle, visualized around 28 days post copulation. Follicular development remained ongoing during early pregnancy. In the males, as in other ruminants, the bulbourethral glands and the seminal vesicles were prominent, whereas the prostate gland was indistinct.Knowledge about the reproductive tract morphology and physiology is necessary for diagnosing medical disorders and abnormalities in giraffes. The aim of this study was to help consolidate the current knowledge on basic reproductive parameters for this species.     

Relationship between androgens, environmental factors and reproductive behavior in male white rhinoceros (Ceratotherium simum simum)

We conducted a longitudinal study of the endocrine activity of free-range male white rhinos. An enzyme immunoassay to measure androgens in the feces was developed and validated to show that it can be used to study testicular activity. We identified two fecal metabolites similar to testosterone and dihydrotestosterone. Several lines of evidence suggest that these metabolites clearly reflect testicular activity. Firstly, the stimulation of testicular activity with synthetic GnRH caused a 156% increase in androgen metabolite concentrations in the feces 1 day after treatment. Secondly, androgen metabolite concentrations increased with sexual maturity in rhinos, and finally there was a correlation between testosterone concentrations in plasma and androgen metabolite concentrations in feces. Using the method that we developed, it was possible to establish whether a relationship exists between androgen metabolite concentrations, the behavior and environmental factors. Adult territorial males (n = 5) had elevated androgen metabolite concentrations during months of high rainfall (September-February) compared to months of little or no rainfall (March-August). The increase in concentrations coincided with the beginning of the rainy season, suggesting a seasonal trend in reproduction. This trend was confirmed by behavior observations showing both a higher frequency of conceptions within the first 4 months of increased androgen metabolite concentrations, and a higher number of inter-sexual conflicts, reflecting the initial aggression between the sexes during the consort period. It was also evident that males accompanying a receptive female had higher fecal androgen metabolite concentrations compared to being alone. The elevated levels were likely induced by female presence.     

The feeding ecology of a selective browser, the giraffe (Giraffa camelopardalis tippelskirchi)

A herbivore can manipulate certain factors of its feeding behaviour in order to achieve the metabolic requirements for reproduction. These factors include the choice of habitat in which to feed, the selection criteria for choosing food items, and the time allocated to feeding or devoted to other energy-consuming activities. The manipulation of these behavioural factors by giraffe in the Serengeti National Park, Tanzania is analysed in relation to the seasonal changes in the quantity and quality of the food resource.
The pattern of habitat choice demonstrates seasonal movements by giraffe across the drainage catena in response to differences in the rates of browse production between woodland types.
Giraffe show a positive inter-specific selection for the minor food items with a low available biomass, and utilize the dominant species in approximate proportion to their availability. Plant part selection is shown for the flushing shoots with very high protein contents.
Selection criteria include a significant selection for phosphorus, and in the dry season a selection for high energy material by breeding females. With the high nutritional qualities of the diets, negative criteria such as secondary chemical compounds are important. Patterns of browse selection are correlated with inter-specific seasonal changes in plant phenology.
Giraffe devote more time to foraging as the biomass and quality of the food declines in the dry season. Energy is conserved by minimizing energy-consuming activities at the most demanding times of day.     

Structure and sympathetic innervation of the intracranial arteries in the giraffe (Giraffa camelopardalis)

Fluorescence histochemistry discloses that the carotid rete mirabile in the giraffe has a poor sympathetic innervation. In contrast, the efferent artery of the rete (internal carotid artery) and the cerebral arteries show moderate sympathetic innervation. A certain degree of regional variability was noted in which the rostral arteries (anterior and middle cerebral) receive more sympathetic nerves than the caudal (posterior communicating and basilar) arteries. The sympathetic nerves on the giraffe cerebral vessels may constitute part of a host of mechanisms by which regional blood flow to the brain is regulated. Conversely, the paucity of sympathetic innervation of the carotid rete mirabile may indicate that this structure does not play an active role in vasoconstrictor responses during postural changes of the head.     

Ovarian cycle phase and same-sex mating behavior in Japanese macaque females

The relationship of the ovarian cycle phase to same-sex mounting activity in adult female Japanese macaques (Macaca fuscata) was studied during the 1997/1998 mating season. Fecal samples were collected from eight female subjects two to three times per week and analyzed by enzyme immunoassay for fecal hormone levels. Hormone profiles of estrone (E1) and pregnanediol (PdG) were used to separate ovarian cycles into three phases: follicular, periovulatory, and luteal. Patterns of same-sex and heterosexual mounting behavior in the females were analyzed for phase variation during conceptive cycles. Same-sex mounting among female Japanese macaques occurred most frequently during the follicular and periovulatory phases of the cycle, and not at all during the luteal phase, paralleling the pattern found in heterosexual mounting behavior. These findings suggest a link between hormonal fluctuations and patterns of sexual mounting, regardless of whether the partner is of the same or opposite sex.     

Testosterone, reproductive stage, and territorial behavior of male and female European stonechats Saxicola torquata

We investigated territorial behavior and circulating testosterone (T) levels in a multiple-brooded population of the European stonechat, a socially monogamous passerine bird with biparental care. Between arrival at and departure from the breeding territories, we (1) quantified behavior of both sexes in response to a simulated territorial intrusion (STI) of a male conspecific and (2) measured plasma T concentrations in males and females. Male response scores to a STI and male T concentrations varied with phase, but there was no temporal association between plasma T levels and the intensity of territorial behavior. During both two sexual and two parental phases, at least half of the tested males showed aggressive responses. About 20% of the tested males responded with courtship prior to laying of the first clutch, but none of the males courted during later phases. Age had a positive overall effect on male plasma T. Females also reacted to the STI of a male, but their responses did not vary with breeding phase. Female plasma T varied with phase, being elevated during production of the first but not of the second clutch. As with males, female responses to the STI were not correlated with T levels. Responses of pair partners were positively correlated with each other. We conclude that modulation of male territorial aggression with breeding phase is not regulated by changes of plasma T concentrations. In light of other studies showing reduced male aggression by pharmacological inhibition of cellular actions of T, we propose that T is permissive for male territorial aggression, but does not mediate short-term changes associated with breeding phase. The function of the high female plasma T concentrations during formation of first clutches could be related to the production of eggs with high concentrations of androgens.