Kirk's Dik-dik Research Articles

Wildlife roadkill in the Tsavo Ecosystem, Kenya: identifying hotspots, potential drivers, and affected species

Roadkill is one of the highest causes of wildlife mortality and is of global conservation concern. Most roadkill studies have focused on wildlife in developed countries such as the United States of America and temperate biomes, but there are limited data for the impacts of roads on wildlife in the African tropics, where road infrastructure development is projected to grow rapidly in natural environments and conservation areas. The Tsavo Conservation Area is an important biodiversity hotspot in eastern Kenya and is bisected by a major highway and railways that connect the port of Mombasa to the interior. Along this infrastructure corridor, roadkill was recorded for 164 days over an 11-year period (2007–2018). In total, 1,436 roadkill were recorded from 13,008 km driven of a 164.42 km Nairobi-Mombasa road representing 0.11 collisions per kilometer. The majority of roadkill were small to medium sized mammals (<15kg) (53%; n = 756), whereas birds comprised 32% (n = 460), reptiles 10% (n = 143), with the remaining 5% (n = 77) being large mammals (>15kg). Of the 460 birds recorded, 264 were identifiable represented by 62 species. All large mammals comprising 10 species were identified, including the African elephant, Loxodonta africana and the endangered African wild dog, Lycaon pictus. Thirteen species of small mammal were also identified dominated by Kirk's dik-dik (Madoqua kirkii). Reptiles were represented by 11 species which were identified to the species level. Roadkill hotspots were identified using a kernel density method. The spatial distribution of roadkill was associated with adjacent shrub vegetation and proximity to permanent and seasonal rivers, and differences in seasonality and habitats were observed. Roadkill was lowest on road sections that traversed settled areas as opposed to roads adjacent to the protected areas. The results demonstrate that roadkill for two of the taxonomic groups - mammals and birds - appear high with numerous species detected in the Tsavo Conservation Area. These results can be used to focus efforts to reduce wildlife mortality by guiding future mitigation efforts.

Long-term persistence of wildlife populations in a pastoral area.

Facilitating coexistence between people and wildlife is a major conservation challenge in East Africa. Some conservation models aim to balance the needs of people and wildlife, but the effectiveness of these models is rarely assessed. Using a case‐study approach, we assessed the ecological performance of a pastoral area in northern Tanzania (Manyara Ranch) and established a long‐term wildlife population monitoring program (carried out intermittently from 2003 to 2008 and regularly from 2011 to 2019) embedded in a distance sampling framework. By comparing density estimates of the road transect‐based long‐term monitoring to estimates derived from systematically distributed transects, we found that the bias associated with nonrandom placement of transects was nonsignificant. Overall, cattle and sheep and goat reached the greatest densities and several wildlife species occurred at densities similar (zebra, wildebeest, waterbuck, Kirk's dik‐dik) or possibly even greater (giraffe, eland, lesser kudu, Grant's gazelle, Thomson's gazelle) than in adjacent national parks in the same ecosystem. Generalized linear mixed models suggested that most wildlife species (8 out of 14) reached greatest densities during the dry season, that wildlife population densities either remained constant or increased over the 17‐year period, and that herbivorous livestock species remained constant, while domestic dog population decreased over time. Cross‐species correlations did not provide evidence for interference competition between grazing or mixed livestock species and wildlife species but indicate possible negative relationships between domestic dog and warthog populations. Overall, wildlife and livestock populations in Manyara Ranch appear to coexist over the 17‐year span. Most likely, this is facilitated by existing connectivity to adjacent protected areas, effective anti‐poaching efforts, spatio‐temporal grazing restrictions, favorable environmental conditions of the ranch, and spatial heterogeneity of surface water and habitats. This long‐term case study illustrates the potential of rangelands to simultaneously support wildlife conservation and human livelihood goals if livestock grazing is restricted in space, time, and numbers.

Community-based wildlife management area supports similar mammal species richness and densities compared to a national park.

Community‐based conservation models have been widely implemented across Africa to improve wildlife conservation and livelihoods of rural communities. In Tanzania, communities can set aside land and formally register it as Wildlife Management Area (WMA), which allows them to generate revenue via consumptive or nonconsumptive utilization of wildlife. The key, yet often untested, assumption of this model is that economic benefits accrued from wildlife motivate sustainable management of wildlife. To test the ecological effectiveness (here defined as persistence of wildlife populations) of Burunge Wildlife Management Area (BWMA), we employed a participatory monitoring approach involving WMA personnel. At intermittent intervals between 2011 and 2018, we estimated mammal species richness and population densities of ten mammal species (African elephant, giraffe, buffalo, zebra, wildebeest, waterbuck, warthog, impala, Kirk's dik‐dik, and vervet monkey) along line transects. We compared mammal species accumulation curves and density estimates with those of time‐matched road transect surveys conducted in adjacent Tarangire National Park (TNP). Mammal species richness estimates were similar in both areas, yet observed species richness per transect was greater in TNP compared to BWMA. Species‐specific density estimates of time‐matched surveys were mostly not significantly different between BWMA and TNP, but elephants occasionally reached greater densities in TNP compared to BWMA. In BWMA, elephant, wildebeest, and impala populations showed significant increases from 2011 to 2018. These results suggest that community‐based conservation models can support mammal communities and densities that are similar to national park baselines. In light of the ecological success of this case study, we emphasize the need for continued efforts to ensure that the BWMA is effective. This will require adaptive management to counteract potential negative repercussions of wildlife populations on peoples' livelihoods. This study can be used as a model to evaluate the effectiveness of wildlife management areas across Tanzania.

A new species of sucking louse (Phthiraptera: Anoplura: Linognathidae) from Günther's Dikdik (Madoqua guentheri) in Kenya.

Linognathus samburi n. sp. is described from adult male and female specimens collected from a juvenile female Günther's dikdik (Madoqua guentheri) live-trapped near Olturot Village, Samburu district (Rift Valley Province) in northern Kenya. The new species is distinguished from other species of Linognathus including Linognathus geigyi and Linognathus damarensis, both of which parasitize Kirk's dikdik (Madoqua kirkii). A dichotomous key to the species of Linognathus that are known to parasitize dikdiks is included.

Tuberculosis infection in wildlife from the Ruaha ecosystem Tanzania: implications for wildlife, domestic animals, and human health

Mycobacterium bovis, a pathogen of conservation, livestock, and public health concern, was detected in eight species of wildlife inhabiting protected areas bordering endemic livestock grazing lands. We tested tissues from 179 opportunistically sampled hunter-killed, depredation, road-killed, and live-captured wild animals, representing 30 species, in and adjacent to Ruaha National Park in south-central Tanzania. Tissue culture and PCR were used to detect 12 (8.1%) M. bovis-infected animals and 15 (10.1%) animals infected with non-tuberculosis complex mycobacteria. Kirk's dik-dik, vervet monkey, and yellow baboon were confirmed infected for the first time. The M. bovis spoligotype isolated from infected wildlife was identical to local livestock, providing evidence for livestock-wildlife pathogen transmission. Thus we advocate an ecosystem-based approach for bovine tuberculosis management that improves critical ecological functions in protected areas and grazing lands, reduces focal population density build-up along the edges of protected areas, and minimizes ecological stressors that increase animals' susceptibility to bovine tuberculosis.

Fire history and management as determinant of patch selection by foraging herbivores in western Serengeti, Tanzania

Although the use of fire as a management tool has increased during the past decades in East African savannas, there is insufficient knowledge about herbivores' utilization of areas with different fire history. We therefore examined large mammal herbivores' preference for patches that differed in fire history to test whether herbivores would non-randomly select patches according to availability. Our study area was the East African Serengeti ecosystem. Animals were recorded along transects at monthly intervals from May 2001 to April 2006, and data on the burnt and non-burnt areas along transects were extracted from existing fire maps. The prediction was tested using chi-square goodness-of-fit test, and selection ratio as a preference index for patch types. Our results show that African buffalo persistently occurred in non-burnt patches, whereas browsers (Giraffe and Kirk's dik-dik) and mixed feeders (Grant's gazelle and impala) were often seen in non-burnt patches but also used burnt patches. Grazer species (Thompson's gazelle, topi, wildebeest and Burchell's zebra) favoured patches burnt in the current year compared to non-burnt patches. For all species together, patches burnt repeatedly were least selected compared to those that were burnt only once in 3 years. The outcome of this study suggests that annual burning of the same patches is not optimal for biodiversity maintenance and ecosystem functioning.

A preliminary study of sex ratios in captive‐born ruminants

There are a number of studies reported in the literature which suggest that in the wild, body size and condition of ♀ ruminants can affect the sex ratio of offspring. The physical condition of a ♀ can be affected by factors such as nutrition, age, stress, population density and social status. This paper describes a preliminary study of sex ratios in the offspring of 17 species/subspecies of ruminant, using data obtained from regional and international stud‐books. The total number of ♂ and ♀ offspring were compared with the expected equal sex ratio via Chi‐square analysis for each species/subspecies. The overall sex ratios of 16 specieshbspecies studied did not significantly differ from50:50, which indicates that any effects of maternal condition may cancel each other out at the population level. Kirk's dikdik Mudoyua kirkii was the only species found to have a skewed sex ratio, with more ♂♂ born than ♀♀. The results of this preliminary study are welcome in light of attempts to maintain genetically viable and demographically stable populations in captivity.

Female dispersion and the evolution of monogamy in the dik-dik

In facultatively monogamous mammals, females are thought to be too widely dispersed for males to defend more than one female range. We tested this hypothesis in a monogamous antelope, Kirk's dik-dik,Madoqua kirkii.Dik-dik territories were compared across three indices of quality to investigate whether males are monogamous because of constraints on the area, or resources, that they are capable of defending. Territories varied substantially in size and quality, with some containing up to five times the resources of others. Moreover, the territories of four temporarily polygynous males were not of higher quality than those of monogamous males. These results are inconsistent with the idea that dik-diks are facultatively monogamous: males can, and often do, defend enough resources and sufficient area to support two or more females. We investigated the relationship between resource dispersion and monogamy further by providing food to territories over a 3-month period. Although provisioned pairs obtained 20% of their daily requirements from the food, there was no change in the territory size of either sex. Female dispersion does not account for monogamy in the dik-dik; instead we argue that monogamy has evolved as a result of male mate guarding.

Genetic and behavioural evidence of monogamy in a mammal, Kirk's dik-dik (Madoqua kirkii).

Little is known about the mating behaviour of monogamous mammals. Here, we present behavioural and genetic evidence of fidelity in a socially monogamous dwarf antelope, Kirk's dik-dik. DNA microsatellite analysis revealed no evidence of extra-pair paternity (EPP) in dik-diks: mothers' partners matched the paternal genotype in all 12 juveniles tested. One likely reason for the absence of EPP is that males guard their mates closely during oestrus and over-mark all female scent, thereby reducing the likelihood of other males attempting to mate. In addition, males may be limited in their ability to search for extra-pair populations (EPCs) by activities associated with pair-bond maintenance. Year-round, males maintained proximity within pairs, followed their females' activity patterns, and spent approximately 64% of their time with their partners. However, males did attempt to obtain EPCs when the opportunity arose, and genetic monogamy in dik-diks is probably best explained by the behaviour of females: in contrast to many monogamous female birds, female dik-diks do not appear to seek EPC partners. We propose that females avoid extra-pair males because they are unable to mate with them without instigating a potentially dangerous conflict.

Monogamy without biparental care in a dwarf antelope

The only widely accepted explanations for the evolution of monogamy in mammals have been based on the benefits of biparental care of offspring. This is probably because, unless biparental care is important, the most competitive males would be expected to monopolize more than one female. This study investigates whether males are important for offspring survival in a monogamous dwarf antelope, Kirk's dik-dik (Madoqua kirkii), by testing three hypotheses that have been proposed to account for monogamy in mammals. In dik-diks, males could help their mates and young by: (i) defending resources; (ii) defending against infanticide by other males; and (iii) reducing predation risk. Because territorial defence was mainly sex-specific, males did not defend resources for their mates or offspring. Males also made no attempt to kill infants they had not sired, so there is no risk of infanticide. Nor was there any evidence that males reduced predation risk: females were not alerted to an approaching predator sooner when males were present, and only mothers responded to playbacks of the call of a predator which preys on juvenile but not adult dik-diks. This is the first conclusive evidence of the absence of paternal care in any monogamous mammal.

Conflicting Territory Use in Males and Females of a Monogamous Ungulate, the Kirk's Dikdik

AbstractIn monogamous mammals it is often unclear why males do not defend larger territories to attract more than one female. I investigated the territoriality of the monogamous Kirk's dikdik, Madoqua kirki, a dwarf antelope, in which food resources increase with territory size and some males defend enough resources for more than one female. Yet, all males are paired monogamously. When males were removed from small territories, their female partners spent more time outside of their territories than females in large ones. When females were removed, their male partners almost never left. Pairs in small territories spent more time together than pairs in large ones. Paired males left mostly together with their females, apparently not on their own initiative. Presumably because females in small territories left more often, their males spent more time outside in the female's company than males in large territories. I argue that males in smaller territories can keep better track of their females and that they can effectively reduce their females' time outside. Male intrusion pressure was unrelated to territory size, but it increased in the presence of unguarded females. If large territories decrease the ability to mate guard, and if unguarded females attract competing males, then defending large territories may be uneconomical, even it they could attract more than one female. On the other hand, territories must be large enough to satisfy the requirements of a single female.

Monogamy in the dik-dik

Kirk's dik-dik ( Madoqua kirki) is one of several ungulates for which field studies have confirmed monogamous pair bonding. Kleiman has discussed two forms of monogamy, obligate and facultative, which differ in the strength and frequency of pair-bond behavior patterns. This paper examines the nature of the pair bond in Kirk's dik-dik with respect to these behavioral criteria. Pair formation and the pair-bond relationship was observed in 4 pairs of captive-born dik-dik at the National Zoological Park in Washington, DC, U.S.A. Quantitative data on pair-bond strength as measured by interaction rates, behavioral synchrony, and proximity were collected. These dik-dik exhibited features typical of a facultatively monogamous species. The pair bond was quickly established. Pair members typically interacted infrequently and the male assumed most of the responsibility for territorial maintenance. Males scent-marked significantly more often than females. Pair members maintained close proximity and exhibited a moderate degree of behavioral synchrony. The results are discussed with reference to studies of two other monogamous antelopes, klipspringer ( Oreotragus oreotragus) and blue duiker ( Cephalophus monticola).

Patterns of muscular growth in the African Bovidae

Three types of anatomical data (body composition, regional muscle proportions, segmental distribution of body mass) are compared for neonates and physically mature individuals from 4 genera of African Bovidae. The data reveal (1) fundamental differences in the adults which correlate directly with their locomotor patterns, and (2) differences in the newborns which correlate with developmental strategy. “Lying-out” species such as Kirk's dik-dik ( Madoqua kirki), dorcas gazelle ( Gazella dorcas) and sable antelope ( Hippotragus niger) possess only two-thirds of the muscle at birth than they do as adults, whereas a newborn “follower”, such as the brindled gnu ( Connochaetes taurinus), has proportionally as much muscle (40% of weight) as it has as an adult. This suggestive relationship begs further investigation. In all species muscular growth shifts the center of gravity towards the hip joint, a more optimal biomechanical position.

Assessment of permanence and stability in the territories of Kirk's dikdik (Rhynchotragus kirki) in Tanzania

ABSTRACTThe permanence and stability of 20 territories of the dikdik Rhynchotragus kirki, were studied at Arusha National Park Tanzania. Response criteria included the structure, size and vegetation attributes of territories, density of dikdik, and spatial distances between neighbouring territories. Fourteen of the territories studied were spatially fixed and stable while six were unstable. Two of the unstable territories were completely abandoned. Mean territory size was 0.11 and 0.13 ha during the rainy and dry seasons, respectively. 14.2% of circular territories and 42.9% of elliptical and kidney-shaped territories were stable. The figure of 55 dikdik km−2 sighted during morning censuses was lower than that for evening censuses by 13.5%. Spatial distance between territories ranged from 4.5 m to 100 m, an indication that population density might be a function of the size of suitable habitat. Although shrub canopy cover within stable territories decreased by 44.6% between 1982 and 1987, and some territories were realigned with changes in rainfall pattern, pair-bond was maintained by dikdik in 70% of the territories studied.

Effects of reduced shrub density and cover on territory size and structure of Kirk's dikdik in Arusha National Park, Tanzania

SummaryEffects of reducing food and cover resources on territory size and structure of Kirk's dikdik were studied in Arusha National Park, Tanzania.Results show that territory shapes, structure and sizes in Kirk's dikdik vary considerably from one family to another. Comparatively small territory sizes are reported in this work (Mean size = 0.05 ha, SD = 0.02, n= 20). Territories are generally established in the more open areas, and most areas of dense thickets and shrubs are avoided. Reducing shrub density and cover within the territories led to either boundary extension or complete territory abandonment. Such responses by most dikdik families occurred when at least 40% of the total initial shrub density had been removed. These observations are attributable to the concept of economic defendability of territories in animals.RésuméOn a étudié dans le Pare National d'Arusha en Tanzanie les effets de la réduction des ressources alimentaires et du couvert sur la taille et la structure du territoire chez le dikdik de Kirk. Les résultats montrent que la forme, la structure et la taille du territoire du dikdik de Kirk varient considérablement d'une famille à l'autre. Des tailles de territoires comparativement faibles sont rapportées dans ce travail (taille moyenne = 0.05 ha, DS = 0.02, n= 20). Les territoires sont établis généralement dans des zones plus ouvertes et la plupart des zones de buissons et arbustes denses sont évitées. La réduction de la densité de buissons et du couvert dans les territoires mène soit à l'extension des limites soit a l'extension des limites soil à l'abandon complet du territoire. Ces types de réponses de la plupart des families de dikdik survinrent lorsqu'au moins 40% de la densité initiale de buissons fut supprimée. Ces observations peuvent être mises en relation avec le concept de ‘defendabilitééconomique’ chez les animaux.

Defecation rates, pellet and pellet group sizes of Kirk's dikdik in Arusha National Park, Tanzania

Defecation rates, pellet and pellet group sizes of Kirk's dikdik in Arusha National Park, Tanzania

Thermoregulation and oxygen consumption in Kirk's dik-dik ( Madoqua kirkii) at ambient temperatures of 10–45°C

1. 1. Thermoregulatory and metabolic responses of dik-dik ( Madoqua kirkii) were measured over an ambient temperature ( T a ) range of 10–45°C. 2. 2. The lower critical temperature was estimated at T a 25°C. 3. 3. At T a 40 and 45°C, dik-dik panted and oxygen consumption fell below that measured at thermoneutrality. 4. 4. The dik-dik appears well adapted to a high T a but can cope with a low T a only at a high metabolic cost.

Comparison of voluntary food and water consumption and digestion in Kirk's dikdik and suni

SummaryVoluntary food and water consumption of Kirk's dikdik (Madoqua kirki) and suni (Nesotragus moschatus) was determined under controlled laboratory conditions. Both species consumed large amounts of dried matter (lucerne hay leaves) per day. Dry matter consumption of dikdik accounted for 3.8 ± 0.5% and of suni for 3.5 ± 0.2% of body weight. Dry matter intake in one immature dikdik and one female dikdik during late pregnancy and lactation was considerably higher.Dikdik drank very little water (278 ml/day, equalling 83 ml/kg0.82) which is further proof of their adaptation to arid environment. Suni drank about twice as much (401 ml/day, equalling 155 ml/kg0.82), but individual variation of water con sumption was high. Thus, the forest‐dwelling suni seems to be less adapted to de hydration than the dikdik.There was no difference in the digestibility of dry matter and gross energy of lucerne hay leaves for dikdik and suni. The fraction of N‐free extracts which consists mainly of soluble carbohydrates was digested very well (84% and 81%, respectively), whereas fibre and cellulose digestibility was poor. Suni digested crude protein, minerals and cellulose significantly better than dikdik.

Changes in a population of dikdik, Madoqua (Rhynchotragus) kirki (Günther 1880).

In 1968/69 a small local population (deme)--11 to 17 animals on 42 ha--of Kirk's Dikdik was studied in the Serengeti area, East Africa. All animals were known individually and all territorial boundaries mapped. The population was revisited in 1972 and all animals and boundaries were recorded anew. 6 animals of 1968 were still present in 1972, 6 had disappeared and 4 were new. 2 territories were still the same, 1 had been divided up between 2 neighbouring ones, 1 had gained 1 ha. In the following summary of the results the generally formulated statements like "Dikdik do" always are short and stand for the specific statements like "the observed Kirk's Dikdik of the Soit ol Modison deme did". 1. Dikdik live in pairs in territories.--2. The young are expelled from the parental territory at the age of 6 to 9 months.--3. They then are able--nearly fully grown, but the horns of the male male only half of their final size--to establish their own pairbond and territory.--4. The female can produce her first young at the age of 15 to 18 months and is reproductive up to at least 6 years.--5. While the reproductive potential is 2/female/year (gestation period 25 weeks), the realized rate of raised animals in 1968/69 was 1/female/year.--6. Average population age lies around 5 years.--7. Maximum physiological age is 10 or more years.--8. The pair bond is independent of the territorial bond and lasts for life.--9. The territorial bond is independent of the pairbond but does not last for life.--10. Strategical lines of the territorial boundaries are marked by dung areas. The families of both territories each use their own places on these areas. The whole family urinates and defaecates together (one after the other) in a ritualized way.--11. The territorial boundaries can shift. The number of dungplaces along a disputed and/or shifting boundary is higher than along an undisputed stable one.--12. Only the male defends the territory and chases off the grown up male young.--13. The female who does not defend the territory is nevertheless bound to it directly, not only by her bond to the male.--14. The most important open question with respect to the social organization is: How is the grown up female young induced to leave the territory? Can there be circumstances when she can stay?

Observations on the histomorphology of sarcosporidian cysts of some East African game animals (Artiodactyla).

The histomorphology of formalin-fixed micro and macrosarcosporidian cysts of Grant's, Thomson's gazelle, impala, wildebeest, Bubal hartebeest, Cape eland, red duiker, Kirk's dik-dik, defassa waterbuck, Bohor reedbuck, African buffalo, giraffe, warthog, and giant forest hog is described. The wall of microsarcosporidian cysts is smooth and without villi or with villi. The villi are solid or of honeycomb-like structure on tangential sections. In some animals, microsarcosporidian cysts of almost the same diameter with different wall structure were found in the same muscle of the same animal. Some muscle cells contained two or three microsarcosporidian cysts. The wall of macrosarcosporidian cysts of different game species showed also different structure.