Lion demographic profiles in the southern regions of Kruger National Park

Intrinsic (van Orsdol et al. 1985, Packer et al. 2005) and extrinsic (Ogutu et al. 2005, Woodroffe & Frank 2005, Loveridge et al. 2007) factors influence carnivore dynamics. Extrinsic influences such as that of introduced diseases may lead to local extinctions (Kissui & Packer 2004). In Kruger National Park, bovine tuberculosis invaded the buffalo population (Bengis et al. 1996). The prevalence in buffalo is spreading, but dynamics are not substantially altered – buffalo is a maintenance host of BTb (Caron et al. 2003). The infections transferred to lions with high incidences noted particularly in the southern parts of Kruger.

The short- to medium-term effects on the dynamics of lion seems to be unaffected (Keet 2008), once the effects of prey biomass has been accounted for (Ferreira & Funston 2009), the concern is the likely consequences of synergistic effects – e.g. accentuated BTb effects during relatively dry periods or in association with other diseases like FIV already present in the population (Keet 2008). In addition, the existing studies of Keet (2008) and Ferreira & Funston (2009) suffer from survey design and/or assumptions that limit the complete evaluation of BTb effects on lion population dynamics, and in particular future risks of population declines. For instance, Ferreira & Funston (2009) assumed stable age distributions in their calculations of survival rates. Keet (2008) followed individual prides in the northern and southern sections of the Park which has very different incidence of BTb in prey and lions, but he cannot account for differences in prey biomass. The upshot is that lion populations may be affected, but current information does not allow detection of that effect.

This conclusion was reiterated at a recent workshop that aimed to evaluate the consequences of BTb for lions through direct and indirect mechanisms. Outcomes from the workshop were limited due to several input data being absent, guessed or derived making several assumptions. Critical population variables were not readily available, including fecundity and survival schedules. Most of these were derived (e.g. region-specific survival rates, Ferreira & Funston 2009), based on small sample sizes (e.g. adult survival rate, Keet 2008) or old and localized (e.g. reproductive variables, Smuts 1976). Kruger still has a risk of declining lion populations for several reasons, albeit low, that may de-stabilize predator competitive interactions as well as predator-prey relationships. Such changes will directly contrast the objectives of Kruger.

To address this, we propose simultaneous evaluation of the numerical features of several large carnivores. One of these is a Lion Population Research Programme that has several elements proposed to be completed as separate projects.

1. The first project was a lion survey completed in 2008 that followed up on the original Park wide survey in 2005/2006 (Ferreira & Funston 2009) to define population estimates and structure associated with quantifying the incidence of BTb presence in lions.
2. A second initiative comprises five years of focal sampling of prides across study zones of different BTb prevalence in prey and prey biomass.  BTb status of prides will be evaluated at the start of the study.
3. The final initiative focus on a survey in the final year of focal sampling of prides re-estimating lion population sizes and structure in the study zones. This will allow SANParks to evaluate how lion dynamics changed across areas that had different levels of BTb and prey availability, but also across lion prides that experienced different rates of lion infections.  The existing data collected by Keet (2008) over a long time can serve as additional data in the time series of lion-disease interactions.

This proposal focuses on the second aspect of the Programme and aim to define population demography of lions across Kruger National Park within the same zones that Ferreira & Funston (2008) sampled in 2005/2006. In addition, spatial consequences on lion behaviour are key aspects that may drive prey responses to lions, interactions with other carnivores and interactions with each other. These interactions may have potential consequences on the disease dynamics itself. This demographic evaluation will contribute to several parallel studies on other carnivore species that are ongoing at present. Most importantly, the definition of demographic variables will provide information on how to potentially measure outcomes of adaptive management or thresholds of potential concern that is at present central to how SANParks manage ecosystems (Biggs et al. 2003). The data will feed directly into population models defined at a recent lion workshop.

We have structured the second aspect into three projects for logistical and financial reasons. These include:

1. The Northern Project comprises of 10 prides in the low BTb-prevalence-in-prey zones north of the Olifants River. This project has been funded partially through the Park Development Fund of SANParks and contributes to an ongoing study on human-lion conflicts, the first phase of which is defining the magnitude of human-lion interactions, and which is nearly completed.
2. The Central Project in the medium BTb-prevalence-in-prey zones between the Sabie and Olifants River. An ongoing project by the University of the Witwatersrand is following 3 prides, while Panthera, an international organization has been approached for funding costs associated with following 7 more prides.
3. The Southern Project comprising 10 prides in high BTb-prevalence-in-prey zones south of the Sabie River is the focus of this proposal.

Objectives

1.       To estimate fecundity and survival schedules of lions in southern Kruger by observing focal prides in zones of high prey availability and high BTb incidences in prey.

2.       To estimate the incidence of TB in focal prides and how these change over time.

3.       To define spatial use of lions in Kruger by placing GPS collars and defining various home range metrics for focal prides in zones of high prey availability and high BTb incidences in prey.

4.       To evaluate the differential effect of BTb, prey biomass and lion sociality on fecundity and survival schedules.

5.       To evaluate the differential effect of BTb, prey biomass and lion sociality on spatial use through relating spatial data from GPS collars to prey distribution, other lions and environmental variables.

Key Questions

1. What is the age at first birth, litter size, birth interval and age at last birth for lion prides in zones of high prey biomass and high BTb prevalence in prey?
2. What is the incidence of TB and other diseases in lion prides and how do these change over time?
3. How do age at first birth, litter size, birth interval and age at last birth associated with BTb, prey biomass and lion sociality?
4. What is the home range size, intensity of use within home ranges, overlap and movement rates of lion prides in zones of high prey biomass and high BTb prevalence in prey?
5. How do home range size, intensity of use within home ranges, overlap and movement rates of lion prides associate with prey distribution, other lions and environmental variables?
6. What demographic measures predict lion persistence consistently?
7. How can these be incorporated in a Threshold of Potential Concern?
8. What are the management implications?

Work Procedure

The project will make use of lion prides marked with GPS collars placed on 10 prides in the area south of the Sabie River that is a high BTb-prevalence-in-prey-zone.  To address Key Question 1, our survey will observe collar individuals for at least three days every two months for a five year period identifying, assigning age and recording presence of individuals and new individuals such as cubs. From these we will derive age-specific fecundity and survival schedules and compare these between different zones addressing Key Question 3.

At the time of collaring and collar replacements, several veterinary samples will be used to determine the TB as well as other disease status of individuals allowing us to answer Key Question 2.

The GPS collars provide spatial data from which will calculate home range metrics in addressing Key Question 4.  In the final instance we will relate spatial explicit prey, environmental and lion data to spatial metrics to address Key Question 5.

Who is the project being undertaken for?

What are the phase time scales?

1)       Fitting of collars – February 2010

2)       Establishment of field assistant – February 2010

3)       Annual field surveys

Duration of the project?

Who will benefit from the project being achieved?

Who is the funding provider and what is the cost?

How will the study benefit the National Park objectives?

It will contribute to Kruger’s overall predator objective of understanding the role of predators and maintaining large mammal predator-prey relationships as important components of functional biodiversity conservation.  It will also address the alien impact objectives through the effect that an alien disease may have. This addresses the objective of evaluating long-term impact of alien species.

What assistance is expected from SANParks?

Accommodation and permission to use management roads and occasional off road driving.

Activities in study area

Collaring lions in the central regions. Night- and day-time finding of lions and making observations from tourist and management roads.

Description of animals/plants/people

Handling of animals/plants

Lions will be captured using standard call-up baiting techniques. VWS will provide the veterinary services.

Collecting & voucher specimens

Major Milestones

1)       Completion of collaring by March 2010.

2)       Completion of fieldwork.

3)       Final report

Project Risks

1)       Low risk of human injury when capturing and following lions.

2)       Survival rates of lions and collar failures.

Environmental Impact