Giraffe Population Dynamics and Conservation Threats in Murchison Falls National Park
As the seasons progress and landscape responds, we have returned to Murchison Falls National Park to continue our ongoing giraffe population studies. After a few days in the capital city, the open skies and broad horizons of the Ugandan bush offer a welcome contrast to the vehicles and concrete. The change in mentality is almost instantaneous, as we transition to the daily rhythm of field work. On the northern banks of the Victoria Nile, the landscape is verdant. Having just experienced several months of wet season, the plants have responded with remarkable vigor; green leafy trees and tall swards of grass have certainly taken advantage of the abundance of water. Areas that were easily drivable during the dry season surveys have since become impassably quagmired and the termite mounds that were so perceptible a few months prior are once again masked by the tall grasses that erupt from the parched earth following the rains.
According aerial surveys conducted by the Uganda Wildlife Authority, the giraffe population in Murchison Falls National Park has increased at a remarkable rate over the past two decades. The current population of Rothschild's giraffe in Murchison Falls National Park is estimated to be nearly seven times what it was in the early 1990's. This population growth sharply contrasts continental trends over the same time period, with giraffe populations across Africa experiencing notable declines. Given the increases of this endangered subspecies, one of the objectives of our study is to examine potential shifts in demographic parameters over space and time and to evaluate environmental influences on these processes. Understanding the factors contributing to a growing giraffe population can perhaps shed insights into mitigating the population declines seen elsewhere throughout Africa.
We have been conducting seasonal surveys of giraffe populations of Murchison Falls National Park at four month intervals since July 2014, and have returned to continue this growing and increasingly valuable data set. Taking advantage of the unique spot patterns of every individual giraffe, we employ non-invasive photographic s sampling to track survival, recruitment and individual space use across multiple seasons. For long-lived animals with relatively long generation times, population ecology studies benefit from longer-term data collection and monitoring, with robust inferences on population trends only emerging after carefully considered long term studies.
Additionally, by mapping the shifts in distribution of giraffe density over the seasons, we can understand how giraffe utilize the landscape and how these preferences may be influenced by the changing resource distribution that accompany seasonal transitions. Unlike the dry season, when giraffe groups are typically smaller and more scattered over the landscape, during the wetter seasons, we regularly encounter large groups of giraffe - sometimes exceeding 70 individuals.
Even the most carefully considered and meticulously designed empirical study is useless without quality data, so we have returned to the bush to deepen our understanding of this population. In addition to the strong support of the Uganda Wildlife Authority's research and monitoring rangers, we also enlisted the assistance of University students from Makerere University in Uganda, who were stationed in the Park for a summer internship and eagerly joined in the project as dedicated field researchers. Completing the team were Tom and Kathy Leiden of the Leiden Conservation Foundation, who travelled to Murchison Falls National Park to lend their experience to the survey efforts. With our research team established, we set out to over the span of 8 days, driving over 1000 kilometres to twice survey the approximately 1600 square kilometers of the Park on the northern banks of the Victoria Nile.
The days in the field typically entail driving fixed routes across the expanse of the park, searching the bush and distant hillsides for giraffe. From 7:00 am to 7:00 pm, we consistently and attentively drive the dusty tracks to locate the remarkably elusive giraffe. As we encounter giraffe, we slowly approach the group off-track and attempt to photograph every individual in every group. Using the unique spot patterns of individual giraffe as an identifying characteristic, we will upload these images into central database and use a specialized computer program to match photographed spot patterns with known giraffe. Our admittedly unattainably ambitious goal is to observe and photographic every giraffe in Park. Historically, however, on any given survey, we observe between 35% and 45% of all known giraffe in this particular population. Although we have yet to process all of the data from these surveys, preliminary results from the data of this survey suggest that we are on pace for one of the more productive field seasons.
In addition to collecting photographs, we also monitor the prevalence and distribution of skin disease in the park and we observe for signs of wounds from poachers' wire snares. These cable snares are indiscriminate traps frequently set along the pervasive waterways to provide meat for the increasing demand for bush meat (see the December 2015 survey for a more detailed description). Since our survey efforts represent the most intensive observation of the giraffe population, we are a reliable source of information regarding the current effects of snaring on the giraffe population for the veterinary staff. Unfortunately, the snares are so pervasive and such a pervasive threat that we regularly observe at least two giraffe per survey with wire snares still attached to their legs or necks. This particular survey was unfortunately consistent with previous surveys as we observed at least three different giraffe with wire snares still attached to their legs in addition to the many giraffe with old scars and snare wounds. We report these snaring incidents to the veterinary team in the park and, when possible, help to track the snared giraffe and assist the veterinary response unit it immobilizing the giraffe, removing the snare and medically treating the individual. On our last day in the field on this trip, we were able to track a giraffe with a particularly gruesome snare wound and relay the coordinates to the veterinary response unit. In typical professional fashion, they responded by quickly mobilizing the appropriate staff and finding us in the bush as we shadowed the wounded giraffe. With the smooth movements of a well-practiced routine, the veterinary team moved in on the wounded giraffe and administered the tranquilizer from a compressed CO2 dart gun. Within a few minutes, the giraffe was showing signs of the drug and the Uganda Wildlife Authority rangers ran to the staggering megaherbivore with ropes to bring the animal to the ground as gently as possible. As soon as the giraffe was down, the team went to work, removing the snare remnants with a large set of bolt cutters and administering antibiotics to limit the risk of infection, all the while monitoring the health of the immobilized giraffe. Working efficiently, the team had treated the giraffe as best as possible and the reversal was administered. The giraffe rocked to her feet and ran off to rejoin the group foraging on nearby Acacia senegal. Seeing the giraffe freed from the weathered cable snare was indeed a satisfying way to end the trip.
As I return to the office with over 1500 photographs taken during the span of the surveys, I look forward to sorting through the data and analyzing. Time in the field is extraordinarily valuable; in addition to the joy of being in the African bush, this time allows us to collect data, liaise with partners on the ground, and make general observations that may inform our approaches to developing conservation strategy and informing our understanding of ecological theory.
9/12/2017 04:44:16 am
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