Lion & Hyaena Populations

Zambezi Valley

Compiled by Steve Pope, Chipembere Safaris

My observations of the lion and hyaena populations in Mana Pools began in 1982

INTRODUCTION

Since the late 1980`s there have been some dramatic animal population fluctuations in world renowned game regions. These include predator population crashes ; brief explosion of prey numbers and unnatural establishment of hyeana packs to the extent that , in some regions, they have changed their habit from scavenging to predation and thereby profoundly affected predator and prey populations . This study reveals these fluctuations and shows that they are a direct result of human influence through culling , poaching , hunting and through food available to animals from camps.

 

1. A BRIEF HISTORY

Impala were culled every year from 1969 until 1973, when the bush war prevented further population reduction operations. By 1980 there was a balance between prey and predator, so that no culling of impala was necessary. This balance lasted until 1989, when the predator populations crashed and the impala population exploded, which coincides with the hyaena packs establishing themselves.

2. ANIMAL POPULATION DYNAMICS

All animal population sizes are directly related and proportional to their food supply. An increase in food supply will mean an increase in that animal population.

In the July 1992 National Geographic, Mr. M G Hornocker, gives an account of his 10 year study of mountain lion. In it he states that a mountain lion's territory is determined by the food supply. This means that the more abundant the prey animals, the smaller the territory. This explains the density of the predator population on the Mana flood plain up to 1989, but raises the question: where were the predators in 1992 when the impala were so numerous they were culled? In a letter dated 23 September 1992, Mr Rob Shattock states that in 5 safaris totaling 35 days he had one sighting of lions, but recorded hyaena in numbers of 11/6/5/9/4. He also states that in 1991 he saw no lions at all.

Mr. Hornocker also states that food supply, hunting and weather determine deer and elk numbers.

His findings demonstrate that an animal population size is relative to food supply in regard to -

  • The healthy predator population up to 1989, their main food source being impala. K M Dunham J. Zool., Lond. (1992) 227 (330-333).

  • the increase in hyaena population
  • the fact that there were so many impala in 1992 because the food source could support them
  • And to the anomaly as to what happened to the predator population with such an abundance of prey, if not affected by hyaena pressure through cub mortality and deprivation of food

During the eighties lions were plentiful on the Mana flood plain . E.g.:-

  • From 1983 until 1989 Chipembere Safaris only had two safaris on which they failed to find lions.

  • In 1990 there were two safaris with no lions . From then on they were lucky to find lions at all during a 4 - day safari

  • In 1992 the animal sightings log book kept at Nyamepi Office showed periods of up to 10 days with no record of lion sightings. These recordings were from all visitors to the Park. The implication being that in a 10-day period there had not been any lion sighting by any visitor is quite disturbing. A study of the log book showed that reports of lion in 1992 had dropped to nearly 25% of reports in 1991 :-

    MAY 1991 - 57 1992 - 29

    JUNE 1991 - 71 1992 - 16

    JULY 1991 - 77 1992 - 17

The hyena population increased during the eighties due to human influence; i.e. unnatural food sources and the Lion population decreased due to Hyaena pressure.

  • In 1985, 4,000 elephants were culled in the Zambezi Valley. An average of 14,7 elephant a day were shot in the vicinity of the flood plain. At this rate of culling, what amounted to hundreds of kilograms of meat was left on skeletons in the bush daily. This is what initiated the increase in hyaena populations.

  • Another unnatural food source which sustained the increase in the hyaena populations during subsequent years was the availability of food from dustbins at all the camps, plus cooler bags full of meat, often stolen from camp sites, especially at Nyamepi.

  • Another abundant and regular source of food for the hyaena was from canoe safari operations. Almost daily canoe safaris would arrive at Nyamepi and off load the rubbish from a 4-day safari consisting of 10 clients. This would be left in the bins and transferred to the open pit rubbish dump, which the hyaenas subsequently fed on.

  • Another contributory source of food was from tourists feeding hyaena for photographic opportunities and their own entertainment.

These sources of food all served to concentrate hyaena packs on the flood plain.

Once the hyaena packs had become established, they became self-sufficient, adopting the same hunting tactics as the Wild Dogs.

The problem is compounded by the fact that to ensure the survival of the species in a normal situation, the lion and prey populations balance themselves. Abundant food equals cub survival, but poor food supply equals cub mortality and reduces predator pressure on the prey species. However the hyaena ensure their survival as a scavenging species by feeding their cubs in a den. This means that if an abnormal situation prevails where hyaena packs deprive lion of their kills then cub mortality accelerates and the lion population crashes. In the same circumstances the hyaena population explodes. This social den habit of hyeana means that their pups are protected from lion . Lion cubs, however, are exceptionally vulnerable to predation by an unnaturally high population of hyeana for the first six weeks of their lives with their mother, before they are old enough to be introduced to the pride .

In a scientific report by Dr. S Cooper, in the African Journal of Ecology. 1991, Volume 29, she notes that the hyaenas would begin mobbing the lions when they outnumbered them by a factor of two. To effect a complete takeover of the kill, the hyaenas had to outnumber the lions by a factor of four. In another study Dr. Cooper shows that hyaena outnumber lions 3 - 1 in Mana Pools and 6 - 1 in Botswana.

In Mr. Keith Begg's letter of 30 May 1995, he mentions that Colleen Zank found that in the course of her Matusadona cheetah study, there is a very high density of lion (prides of 10 - 20) and comparatively far fewer hyaena. It has been noted that in Matusadona buffalo skeletons are intact , whereas in Mana after a couple of days all that can be found is the skull .

Matusadona and Chitake Springs should be regarded as norms, as they both have healthy predator populations. The hyaena at Chitake Springs remain in a scavenging role in low numbers, so that they are no threat to the predators.

Hyaena/lion incident - Mana Pools June 1994 recorded by Mr Miles Bennet:

"Towards the end of June myself and seven others stayed in one of the Mana Pools National Parks lodges for four nights. Game viewing was generally good with the exception of lion. The warden told us that the week before we arrived four lions had killed a buffalo between the lodges and the warden's office - but within an hour of them killing it, had been chased off by at least 20 hyaena. Despite numerous game drives we did not see any sign of lions.

On our last day, at approximately 06.15hrs on the circular road near the eastern end of Long Pool - we came across several excited hyaena running in and out of a dense thicket near the pan. We stopped our two vehicles and switched off the engines. We spotted a lioness hiding in a clump of bushes on the edge of the large open vlei on the north side of the pan and the road, and could hear another male nearby calling to her. A number of hyaena would respond to the lion's calls by rushing out of the thicket to look for the lions, then rushing back into the thicket where there was obviously a kill. Most of the hyaenas had blood on their faces from feeding.

This carried on for some minutes, until the lioness we spotted broke cover and began walking towards the vlei. At once all the hyaenas (we counted 21) left the kill and chased the lioness into the vlei. They surrounded her and took turns attacking her from behind, and as she turned to defend herself, others would attack her from the rear. As this was going on a large male lion ran in from the tree line on the southern end of the vlei to help the lioness. He attacked one of the hyaena, sending it somersaulting for some ten metres, but he too ended up being surrounded with the lioness, being attacked from all sides by the hyaenas. At this stage the young male we had heard calling to the lioness earlier now broke from cover and went to help the two, as did an elderly lioness from the southern side.

A fierce fight erupted between the four lions and 21 hyaenas, with the hyaenas eventually running back across the road to the kill. The lion, all looking exhausted, walked off to the southern tree line where they lay down and rested, before moving off.

The kill was a young elephant, +/- 3 years old, and the hyaena fought amongst themselves for what was left of it. We are of the opinion that the lions made the kill and were chased off by the hyaena.

I have visited Mana Pools at least once a year since 1986 and have noted an alarming increase every year of hyaena activity and a steady decrease of lions."

Miles Bennett

3. THE FULL IMPACT OF HYAENA DEPRADATIONS

In Mr. Gus Mills report on his Spotted Hyaena study in Namibia, he shows that when hyaena hunt, only 1/3 of their kills are adult prey, the rest are young. This fact is portrayed in the documentary "Patterns In The Grass", which depicts the zebra migration in the Savuti Channel. The packs of hyaena hunt foals, while the lion prides hunt adult zebra. This means the hyaena packs account for much larger numbers of prey animals than a pride of lion. Where a pride of lion kill one adult, a hyaena pack will kill four foals, i.e. a ratio of 4 - 1. Ironically, the film blames the decline of zebra herd numbers from 45 000 in 1981 to 7 000 in 1991 on poachers. 38000 zebra poached in 10 years is inconceivable. This impact on prey is the reason why the impala population has not exploded again at Mana which would be expected with a lack of predators.

4. IS THE PROBLEM CONFINED TO MANA POOLS?

Mr. Pete Fick was in a hide at a bait in the Chewore, when he was attacked by a pack of hyaena. Hunters have described a similar trend in the hunting areas, as what happened in Mana Pools. They have all said that in the early '80's, shortly after shooting an elephant or buffalo, a pride of lion would arrive, but that in the late '80's and early '90's, lion were scarce and a pack of hyaena would show up. This decline in lion numbers caused them to voluntarily impose a ban on lion hunting which lasted until the mid 90s. A significant development is that, because hyaena were on licence yhey were hunted more frequently as their numbers increased ; in some cases more than 20 a year . The end result was that when the hyaena population decreased sufficiently the lion population quickly recovered so that lion are now hunted again.

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The documentaries "Patterns In The Grass", "Eternal Enemies", "The Sisterhood", "The Super Predators" and several other similar wildlife films all illustrate packs of hyaena hunting and harassing even strong prides of lion. The food source which established these packs would have come from hunting in the Savuti as depicted in "Patterns In The Grass", where zebra are shot and only the skins taken.

There is an account (confirmed by Pat Kelly) of packs of hyaena in the Luangwa Valley, which appeared after thousands of hippo died of Anthrax spread from cattle in southern Tanzania

There are hordes of hyaena in the Masai Mara in Kenya. It is common knowledge that in the early 1900's Kenya was the venue for most of Africa's hunting. (Roosevelt, Hemmingway, etc.) Large hunting parties would go out on safari for months at a time. It is reasonable to presume that these hunts provided an unnatural food supply to the hyaena.

5. WHAT ROLE SHOULD HYAENAS PLAY?

With their powerful jaws and ungainly gait, it is incredible that they have become regarded as a 'super predator'. With jaws evolved to be powerful enough to crack buffalo bones for the marrow, they are designed to scavenge. For millennia, they have been living off the remains of predator kills and the sick and weak. None of the early hunter's writings, e.g. Frederick Courtney Selous, describe encounters such as the ones depicted in the wildlife documentary, 'Eternal Enemies'. If they had observed such behaviour, they would surely have written about such a fascinating experience.

The 1964 edition of Collier's Encyclopedia states that the hyaena is a carrion feeder ; that it is a solitary roving animal and that a large percentage of its food is from kills by lions, but no hyaena would dare approach until the lion had satisfied its hunger and left the kill.

In the last forty years our concept of hyaena has changed from the above description to believing that what we now see in these recent wildlife films is normal behaviour.

Wherever large packs of hyaena exist, in the history of that area it will be found that hunting , poaching or culling operations have supplied the food source which increased their numbers.

6. SHOULD WE CONTROL HYAENA?

If it is accepted that the hyaena packs established themselves on an unnatural food source supplied by man, and that their increased numbers have impacted on the predator population, then their numbers should be reduced.

At a National Parks meeting it was shown that the lion numbers in the Zambezi Valley hunting concessions have recovered, even though they are hunted, because every year more than 20 hyaena have been been hunted in each of those concessions.

Gordon Putterill conducted hyaena culling operations in Gona-re-Zhou.

IN CONCLUSION

In the case of the Mana flood plain, if the impala population had been left alone in 1992, as an abundant food supply for predators, and if the hyaena population had been reduced to a scavenging role, within a couple of seasons the lion, leopard and cheetah numbers would have recovered.

We have had the privilege of witnessing this phenomenon of a hyaena population evolving from a scavenging to a predatory role in a short period of time. We now have a unique opportunity to realise the far reaching effects of our hunting and culling activities and to correct the misconceptions we have gained in the last twenty years.

If the hyaena numbers are reduced so that they fulfil their natural scavenging role for which they are evolutionarily designed , the prey numbers will quickly recover and the predators will follow.

@Copyright Steve Pope 2002

Lion and Hyaena Populations - Zambezi Valley
Compiled by Steve Pope - Chipembere Safaris
P O Box 9
Kariba
Tel 061 2946
Cell: 011 610 010
e-mail chipsaf@zol.co.zw


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