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In this Issue
Knob Thorn : A Notable Lowveld Tree
Green Wood Hoopoe v Common Scimitarbill
Black-backed Jackal
Observations from our residents
Knob Thorn : a Notable Lowveld Tree - Dave & Bernie Spencer
A dominant species of the Raptor’s View landscape is Knob Thorn, Knoppiesdoring, Senegalia nigrescens, (formerly Acacia nigrescens) particularly visible at this time of the year when trees are in full flower. Even without flowers the tree is easy to pick out in the veld as the trunk and branches are covered with knobs.
Young trees have a distinct yellow appearance, with prominent knobs, downward curved black thorns and bark which flakes off in small pieces. Some young trees also have a “skirt” of armed branches which protects the main stem from damage. As trees mature the lower branches are shed leaving a bare trunk and a spreading canopy. With age the bark darkens and develops a rough, fissured texture.
Leaves of S. nigrescens are also quite distinctive lacking the feathery appearance of other thorn trees. Each leaf has only a few pairs of round leaflets, usually one or two, which leads to a butterfly wing appearance.
Before the flowers emerge the flower buds give the tree a deep red-purple sheen. In our region the long creamy white, sweet smelling flowers appear before the new leaves from July onwards. Trees produce a mass of flower spikes frequently covering the whole canopy, a welcome sight in a dry winter landscape.
Pods of Knob Thorn develop from about November to April changing from olive green to almost black as they ripen. This feature probably gives rise to the specific name “nigrescens” – meaning becoming black. Whilst on the tree the flat pods remain closed only splitting open once they fall to the ground.
At all stages of its growth S. nigrescens plays a valuable ecological role. Baboons, monkeys and giraffe enjoy the flowers. Leaves and shoots are browsed especially by kudu and giraffe and giraffe also eat the pods. The tannin-rich bark is often stripped by elephants. Caterpillars also eat the leaves and are abundant in spring when their droppings may form a visible layer beneath the trees.
Another benefit of the this species is the presence of natural holes used by nesting birds and small mammals. The top of the tree also provides a suitable platform for nests of White-backed Vultures.
Once a tree starts to die back it loses its upper branches, but the termite resistant heartwood allows the trunk to stand for years providing a useful look out perch for birds and animals. ( Great photographic opportunities! ) And finally decomposition begins as fungi and borers break down the wood returning nutrients to the soil.
Senegalia nigrescens belongs to the family Fabaceae, a well represented group on Raptor’s View.
A flowering Knob Thorn in July/August.
Conical knobs with down curved thorns.
A flowering spike of Senegalia nigrescens
Leaves of Knob Thorn showing characteristic paired leaflets.
A bracket fungus on an old Knob Thorn tree, the start of the decomposition process
Natural hole in an old tree, lined with leaves probably used by squirrels.
Green Wood Hoopoe V Common Scimitarbill - Steve Benbow
At a quick glance these two birds with decurved bills and dark plumage could be confused, however there are significant differences between the two species. Although both are arboreal and forage in tree trunks, searching the bark for insects, the species are not related. Green Wood Hoopes belong to the family Phoeniculus while Common Scimitarbills are from the Rhinopomastus family.
Common Animal Signs, Black-Backed Jackal - Ken Farnsworth
The Black-Backed Jackal (BBJ) is recognized by the mantle or ‘saddle’ of black hair tipped with silver on the back that contrasts with the rust-colored body. The tail is also black-tipped. The Black-backed is usually the most frequently seen, as it is more diurnal than the other two species of Jackal found in Africa. They are widespread because they are very adaptable canids whose diet, breeding strategies and social arrangements can be modified to suit its environment. On RV they are both diurnal and nocturnal and are regularly seen along the roads and fence lines in the early mornings, evenings and on overcast days. On cold nights and mornings they might be seen curled up on impala middens for warmth.
Largely because it is poorly understood the BBJ is persecuted as a ‘problem animal’ for small stock farmers. In fact, Jackals are excellent role models for us! These highly intelligent animals lead a social, co-operative existence in which each member of the family display loyalty, courage and generosity –all qualities that we admire. BBJs are also monogamous, and one of the few mammals that form long-term relationships. The social unit mostly seen on Raptors View is made up of the two parents and their young ones. However, they are known to form hunting packs on an opportunistic basis on larger reserves.
Both male and female mark and defend their home territory. They scent mark with urine and faeces—which are often deposited on prominent objects like rocks, clumps of grass etc. These form visual markers along trails and roads and assist in dispersing scent.
Black-Backed Jackal scat on grass tufts. Black when fresh, turning white with age, dog-like.
Black-Backed Jackal scat on dead tree branch. Often on objects (rocks, grass clumps…even our trail markers!)
They spend most of their time searching for food and are opportunistic when it comes to eating, being omnivorous they will eat fruits, insects, rodents, reptiles as well as scavenging. Jackals are also coursing predators (chasing prey down) and searchers (especially of young fawns hiding in the vegetation)—you might observe them inspecting herds of Impala for signs of recent birthing: if so, one Jackal will distract the mother while the other would kill the lamb. In closed reserves such as ours, where dispersal of animals is restricted by fences and which are often only proxies of natural ecosystems, BBJs can potentially threaten the viability of those ungulate species that rely on hiding their fawns as an anti-predator strategy (Duiker, Bushbuck, Steenbok).
This species is highly vocal, and is well known for their characteristic high wailing calls mostly heard in the early evening and mornings—when a chorus of answering individuals can be heard from all around. Also, because of the presence of Leopard on Raptor’s View you will also hear a distinctive call they make as they follow it about the estate (it’s a shorter yapping call with what’s best described as ending in a stuttering bark).
They mate from May to August, with the gestation period lasting for about two months. After mating, the females prefer to give birth to the young in underground vacated ANTBEAR burrows that have more than one entrance for escape. As with domestic dogs, BBJ pups are born blind and without teeth. The youngsters’ eyes open after about 10 days, and their mother stays in the den with them throughout the first few weeks to provide them with warmth, milk and protection.
Front Spoor L and R front foot. The Jackal track shows a pear-shaped or oval shaped form imprinted by the front paw’s large back pad showing 4 toes
Spoor in wet sand – note claw marks. Drawing a cross is easily made between the toes and pads.
Kill patterns. A Jackal usually catches prey by biting its head, and clear tooth marks can be seen between the eye and ear. (Caracal, Leopard etc., use a windpipe bite beneath the jaw). Jackal will remove an animal’s innards but eat the heart, liver, lung and kidneys. They will also leave gnawing marks on bones, in particular the ribs. (Caracal don’t remove the innards and start feeding on the inside hind legs)
Interesting Sightings on the Estate
Beautiful Leopard image from motion camera at 115 Marsh Harrier. Jenny Lombard.
Thirsty bees at the birdbath – Derek Solomon, 254 Martial Eagle
Greater Blue-eared Starling at 254 Martial Eagle. New bird for Raptor’s View. Derek Solomon.
