University of Toronto / Royal Ontario Museum, Canada
Background/Question/Methods
Mammals with slow life histories are at greater risk for extinction than those with faster life histories. Though life history broadly correlates with body size, there is considerable variation among similarly sized species. Additionally, some mammals have been demonstrated to have plastic life history traits. Therefore, species with a slower life history than expected for their body size and/or little ability to adapt their life history strategy may be at greater risk of extinction than would be otherwise expected.
Museum collections may offer an opportunity for exploring how a species' life history has changed over time through bone histology. As most vertebrates grow, they deposit annual growth marks in the cortices of their bones. By counting and measuring these growth marks, we can produce a growth curve that estimates age at death and the weight of an individual throughout its lifetime. However, it is unclear how well these histologically derived growth curves approximate actual body mass growth in many mammalian taxa. Here, we perform osteohistological growth curve reconstruction on a male wild-caught specimen of Panthera leo and compare those results with data derived from osteological measures and observational growth data.
Results/Conclusions
Our histological results closely match those produced using osteology and observational data. Growth modelling suggests that the individual died at the age of 3.6-4.5 years. This agrees with an osteological age estimation of 3-5 years old based on cranial, dental, and epiphyseal features. All growth parameters for our histologically sampled specimen, including asymptotic body mass, age at 95% of asymptotic body mass, inflection point, and maximum daily growth rate, fit within the range of variation seen in growth curves computed from observational growth data. Taken together, these results suggest that growth curve reconstruction using bone histology accurately reflects the actual growth patterns of lions.
The use of museum specimens in life history studies opens various areas of research. Museum specimens may be useful in determining the life history of rare, cryptic, and/or understudied taxa. The historical nature of museum collections also means that researchers can investigate long-term changes in life history, for example in response to anthropogenic influences, even where data were not historically recorded. Such research can allow us to better understand how species responded to environmental change and human impacts in the past, and could improve predictions of how they will respond in the future.
