Attacks on lambs by Scavengers
In the first week of November 2008 a commercial sheep farmer in southern Namibia reported that a flock of about 40 vultures were harassing and killing livestock on a 9000 hectare farm divided into about 45 camps. The farmer was neither able to identify the actual species nor give the ages of the birds but from the report it is assumed that both Whitebacked and Lappetfaced Vultures were implicated. The farmer said that the birds had been on the farm for 10 to 14 days and that they were so intent on the feeding that only after making serious attempts to chase the birds and then firing at them did the birds realize the danger posed by the farmers’ approach. Most fortunately for vulture conservation this farmer clearly did not want to kill the birds. Although he reported predation of lambs and attacks on adult ewes and that his losses were in the order of two animals per day it remained unclear as to whether these losses were newborn lambs or another age group of animals. The farmer did admit that the livestock are not in very good condition, being the end of the dry winter season through which some ewes had carried lambs.
Just two weeks later another bird lamb conflict was reported. This time Black Eagles predating on lambs of sheep and occasionally springbok. These birds are reported to be taking more than one lamb a day and only eating a little off each carcass. The farm is 5000 hecatre and with 800 sheep has is being grazed at a carrying capacity of 1head per 6 hectares. The entire farm is electric fenced and no labor is employed for the sheep.
In southern Namibia the carrying capacity of the land ranges from around 20kg per hectare or 1 small livestock unit per 2.5 to 3 hectare in the Kalahari Gochas and Aranos areas, down to 15kg per hectare or 1 small livestock unit per 4 hecatre in the Stampriet and Kalkrand area. The carrying capacity can be as low as 5,5 -7,5kg per hectare or 1 animal per 6 to 7 hecatare. On the farm where the vultures were reported predating the carrying capacity is at 1 small livestock unit per 5 hectares. This means that in a camp of around 200 hectares about 40 sheep range.
Many, probably most, commercial sheep farmers in Namibia attempt to keep their land absolutely free from mammalian predators. Any sign of a predator results in an immediate mobilization for search and kill. Over the years few farmers have come up with innovative methods of non-lethal herd protection and in some farming communities non-lethal methods of protection from small mammal predation are not even considered because of the assumed negative cost-effectiveness of these methods. Some recommended non-lethal herd protection methods are probably not feasible on large tracts of land with animals grazing far from one another. All non-lethal methods will cost the farmer a fair amount of consistent effort and like most strategies for farming, a combination of methods and the correct timing will influence effectiveness of the desired outcome.
Vultures are described as valuable assistants to farmers when they alert whoever is watching to a livestock death. I have witnessed a party of poachers caught slaughtering cattle in a remote camp because the farmer went to check on the circling birds. When vultures come to feed on a carcass they quickly clean up thereby preventing the spread of disease and the breeding of flies. Besides these positives vultures are also a valuable tourist attraction being part of the large raptors gracing our skies.
By November most breeding Whitebacked and Lappetfaced Vultures will have completed their 2 month incubation of eggs, their 4 – 5 month period of chick on the nest and be somewhere in the period called post fledging dependence. This is whrn the young birds though off the nests are still fed by the parents. Birds newly fledged will remain in the vicinity of the nests older fledglings will start foraging with the adults. Post fledging dependence can last up to 6 months. During the vulture breeding season food requirement is at its highest. Large nestlings will be consuming maximum amounts in the last prefledging growth spurt, young fledged birds pre or just post dependence will be out in nursery groups and not yet widely dispersed. Much of this happens after the dry season and in southern Namibia can commonly be commercial small stock predator-free farms.
The problem for vultures is that without any predators on the land there is little for scavenging birds to clean-up. Natural deaths of domestic stock in a well managed flock will be limited by attention to herd health through vaccinating against known diseases, treating for internal and external parasites, providing adequate grazing and marketing strategies. If a farm manager is maximizing the graze and browse for the livestock not much spare food will be available for wild antelope and those populations will not be able to thrive. Viable commercial livestock farming on land of low carrying capacity requires large farms and preferably more than one farm. Vultures in sheep farming area can face huge tracts of land that provide no food resources for them.
Questions that can be asked are is are vultures learning to predate. This question might also be asked in terms of the feeding at vulture restaurants. Are we falsely increasing vulture populations?
For many years vulture
biologists denied that vultures would predate on livestock. Then more
than a decade ago photographic proof of European Griffons taking livestock
forced a reassessment of potential vulture behaviour. In Namibia predation
has been reported by farmers on a few occasions and although in most cases
photographic proof is lacking, there is a now acceptance that during food-stress
times vultures can predate especially on newborn lambs or kids. However
the condition of the ewes and the new-borns has still to be well described.
If each camp is about the same size that would equal about 200 hectares per camp. The stocking rate in that area is very low from 1 animal to between 2.5 and 4 hectares animals per hectare and so there could be over 2000 sheep on that farm. This farmer is running stock on two other farms in the area and altogether has six employees, 2 per farm one for fence checks and one for water point maintenance.
Ideas to solve the issues are not many but there is the possibility of a traceable wildlife-friendly lamb or sheep There remains a need for a nationally coordinated strategy in Namibia.