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The Truth in the Tooth – Using Science to Judge Lion Ages in the Field

Aug 05, 2014

huntforevertruthtoothNiceMaleLionTen years ago, a seminal scientific paper suggested that lion hunting could be conducted sustainably if only lion males over a minimum age of five years were targeted. Recognizing that field aging of wild lions is difficult and in order to buffer against selection error, the ideal minimum was conservatively raised to six years. And so, the concept of age-based trophy selection to promote sustainable lion hunting was born.

A number of countries now require that trophy lions meet or exceed a minimum age, with stiff penalties such as fines, reduction in quota, or confiscation of trophies incurred for miscalculations. Yet our ability to judge lion age remains imperfect. In short, the practical skills needed to accurately determine lion age have not kept pace with our needs.

Since 2006, the Zambia Lion Project (ZLP) has been collecting data

The Nomad digital x-ray system is completely portable allowing high-quality data to be collected and viewed instantly in the field.
The Nomad digital x-ray system is completely portable allowing high-quality data to be collected and viewed instantly in the field.

on trophy lions taken in Zambia, including trophy photos and assessing physical features that relate to age such as tooth wear, skull suture closure, and tooth x-rays. However, because Zambia’s lion populations are wild and free ranging, exact ages of the sampled lions are not known. Thus, we have had to settle for best estimates based on a range of cues known to change with age in most mammalian species.

One potential solution is to examine the same features in lions whose ages are known, including animals born in captivity. Measurements gathered from wild lions can then be compared and calibrated. In this way, age estimates for wild lion trophies can be vastly improved. For years, this has represented a crucial “missing piece.” Finally in December 2013, a breakthrough occurred when ZLP was invited to South Africa by lion breeders who generously allowed access to study their captive lions.

Not all features are comparable. Captive lions do not experience the same food stresses that their wild counterparts face on a daily basis. They are not subjected to the same physical challenges of having to catch and kill large dangerous species like buffalo, or chew through the tough hide of an elephant or hippo. As a result of constant nutrition and a more sedentary lifestyle, manes of captive lions

Preparing to x-ray a known-age lion that has been anesthetized in South Africa.
Preparing to x-ray a known-age lion that has been anesthetized in South Africa.

develop sooner, bodies grow larger, and their teeth do not show the same levels of wear and tear. Thus, features like mane and body size and tooth wear cannot be directly compared between captive and wild animals.

By contrast, tooth development is a highly conservative trait from an evolutionary standpoint. And, while it remains to be tested, it is believed that the x-ray technology used to relate tooth development to age will be comparable between captive and wild lions. This has broad implications for hunters and guides as tooth x-rays are considered an important component in official lion age assessments.

The inner pulp chamber (dark line down center) of the tooth fills in with advanced age.
The inner pulp chamber (dark line down center) of the tooth fills in with advanced age.

The first known-age lion males in South Africa were darted and their teeth x-rayed in December 2013. Additional skulls were examined at taxidermists’ studios as part of Phase One.

Phase Two of the study entails validating tooth samples of captive bred lions by comparing them with x-rays of known-age lions in wild populations. If as expected, tooth development of captive and wild lions is consistent, then combining samples will provide a large and robust database for further analyses and comparisons.

In Phase Three, findings from ZLP’s studies on aging lions will be summarized both in scientific publications and popular formats making them widely available for education and training purposes.

Zambia Lion Project’s lion aging study is funded in part by Safari Club International Foundation. To learn more, e-mail Dr. White at paw@carnivoreconservation.com.

Status of Trophy Lion Age Programs

Mozambique’s Niassa National Reserve was the first to implement minimum age requirements for trophy lions in 2006. The program is based on the Niassa Points System with penalties such as loss of quota in subsequent seasons for shooting lion males under 6 years of age, or for failing to supply full information from the hunt. In

Obtaining a digital tooth x-ray of an anesthetized known-age lion in South Africa.
Obtaining a digital tooth x-ray of an anesthetized known-age lion in South Africa.

addition, shooting male lions 4 years of age or less, or shooting any lioness results in cancellation of the PH’s license.

Tanzania’s 2010 Hunting Regulations stated, “No person shall hunt lion of an age below six years.” Mandatory sampling and minimum age restrictions for trophy lions countrywide began in 2011. The regulation was amended in December 2013, and a third category of “four or five years” is now recognized. As in Niassa, the younger the lion shot, the greater the penalty. Shooting lions between the ages of 4 and 6 years results in fines and quota reduction. Shooting lions under 4 years of age results in trophy confiscation, fines and a larger reduction in quota in subsequent seasons. Since the minimum age regulation was implemented, the number of lions shot in Tanzania dropped from about 200 animals/year to approximately 60 lions taken in 2013.

Zimbabwe is the latest country to move toward adopting a sampling program and age minimums for trophy lions. As in Niassa and Tanzania, Zimbabwe’s proposed system utilizes points but

Preparing to x-ray skulls of known-age lions at a taxidermist in South Africa.
Preparing to x-ray skulls of known-age lions at a taxidermist in South Africa.

recognizes four age categories instead of three: 6 years and older, 5 years old, 4 years old, and less than 4 years of age. Rational for this age structuring is that shooting trophy lions 5 years of age (minimum) is sustainable. As elsewhere, shooting lions 4 years old or less, or failing to complete hunt return forms results in quota reductions. 2014 will mark Zimbabwe’s first year of mandatory trophy lion sampling.

Zambia’s trophy lion aging program has not yet been officially adopted by the Zambia Wildlife Authority. However, prompt feedback on age estimates by ZLP between 2006-2012 fostered voluntary cooperation. Between 70-90% of all lion trophies taken each year were inspected. The future for lion hunting in Zambia is currently under review, but it is anticipated that if and when it reopens, sampling and a minimum age standard for trophy lions would become mandatory to help ensure long-term sustainability.– Paula A. White, PhD

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