Breeding durations as estimators of adult sex ratios and population size
- 257 Downloads
Adult sex ratios (ASRs) and population size are two of the most fundamental parameters in population biology, as they are the main determinants of genetic and demographic viability, and vulnerability of a population to stochastic events. Underpinning the application of population viability analysis for predicting the extinction risk of populations is the need to accurately estimate parameters that determine the viability of populations (i.e. the ASR and population size). Here we demonstrate that a lack of temporal information can confound estimation of both parameters. Using acoustic telemetry, we compared differences in breeding durations of both sexes for a giant Australian cuttlefish Sepia apama breeding aggregation to the strongly male-biased operational sex ratio (4:1), in order to estimate the population ASR. The ratio of breeding durations between sexes was equal to the operational sex ratio, suggesting that the ASR is not strongly male-biased, but balanced. Furthermore, the short residence times of individuals at the breeding aggregation suggests that previous density-based abundance estimates have significantly underestimated population size. With the current wide application of population viability analysis for predicting the extinction risk of populations, tools to improve the accuracy of such predictions are vital. Here we provide a new approach to estimating the fundamental ASR parameter, and call for temporal considerations when estimating population size.
KeywordsAcoustic telemetry Breeding aggregation Operational sex ratio Sepia apama Viability analysis
We thank Jim Mitchell (Santos Limited) for infrastructure support, and all volunteers for field assistance. Financial support was provided by The Field Naturalists Society of South Australia, Australian Geographic Society, Santos Limited., Mark Mitchell Foundation, and the ANZ Holsworth Foundation.
- Aitken JP, O’Dor RK, Jackson GD (2005) The secret life of the giant Australian cuttlefish Sepia apama (Cephalopoda): behaviour and energetics in nature revealed through radio acoustic positioning and telemetry (RAPT). J Exp Mar Biol Ecol 320:77–91. doi: 10.1016/j.jembe.2004.12.040 CrossRefGoogle Scholar
- Blumenthal JM, Austin TJ, Bothwell JB, Broderick AC, Ebanks-Petrie G, Olynik JR, Orr MF, Solomon JL, Witt MJ, Godley BJ (2009) Diving behavior and movements of juvenile hawksbill turtles Eretmochelys imbricata on a Caribbean coral reef. Coral Reefs 28:55–65. doi: 10.1007/s00338-008-0416-1 CrossRefGoogle Scholar
- Hall KC, Fowler AJ (2003) Fisheries biology of the cuttlefish, Sepia apama Gray, in South Australian waters. FRDC final report. South Australian Research and Development Institute, AdelaideGoogle Scholar
- Trivers R (1972) Parental investment and sexual selection. In: Campbell B (ed) Sexual selection and the descent of man 1871–1971. Aldine Press, ChicagoGoogle Scholar
- Voegeli FA, Pincock DG (1996) Overview of underwater acoustics as it applies to telemetry. In: Baras E, Philippart JC (eds) Underwater biotelemetry. University of Liege, LiegeGoogle Scholar