Reproductive potential of the Taimyr wild reindeer (<i>Rangifer tarandus</i>) in 1987–2021

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Results of a study on the reproductive potential of the Taimyr wild deer in the 1987–2021 are presented. The material for the population analysis was formed by empirical samples of altogether 3695 females 2 to 17 years old each and the initial data from aerial surveys of the Taimyr population. The potential fecundity of the species in this part of the circumpolar distribution range (northern Central Siberia) in 1987–1990 averaged 0.412 ± 0.015 female fetuses per mature female. The potential fecundity, both male and female fetuses, totaled 82.4 fetuses per 100 adult females. The realized reproduction of the population in July 1988 amounted to 75.08 calves, vs 75.31 calves per 100 mature females in July 1990. Hence the infant mortality before calving for that monitoring period was 8.6–8.9%. Given the controlled use of the population resources in 1966–1990 (Soviet period), the linear regression equation for adult females was y = 4.6704x + 140.08 thousand (R2 = 0.5342, Ᾱ =5.2%), the linear trend in the numbers of underyearling calves in the period 1975–1990 being y = 5.15x + 73.9 thousand (R2 = 0.84, Ᾱ = 2.76%, r = 0.24, p 0.05). The maximum “yield” of 142.5 thousand calves was noted for the Taimyr population in the summer of 1988. The potential fecundity of the Taimyr deer decreased in 1996–1998 and amounted to 0.339 ± 0.0362 female fetuses per adult female, vs 0.379 ± 0.0013 in 1999–2006, the realized fecundity in the postnatal period in 2002–2007 was found to be 0.295 ± 0.009 females per adult female, or 59.03 calves (males + females) per 100 adult females; this can be interpreted as elimination from spring to autumn of more than 16 calves per 100 adult females (mortality rate 21.3%). Using a linear regression for the 32-year interval between 1990 and 2021, the numbers of adult deer females dropped to y = –14.36x + 231.14 thousand (R2 = 0.48, Ᾱ = 2.4, rxy= 0.89, p 0.01 (tp = 4.36, p 0.01)). The predicted abundance of adult females based on a completed point forecast for the summer of 2022 is estimated at 116.23 thousand heads, vs 101.86 thousand for the summer of 2023. The trend equation for the juvenile group of Taimyr deer showed the following quantitative characteristics in the 1990–2021 interval: y = –21.35х + 175.51 thousand (R2 = 0.95, Ᾱ = 2.9, rxy = 0.98, p 0.01 (tp = 11.01, p 0.001)). Changes in the characteristics of the natal group are negative, as the existing rates of reproduction in the population do not balance its decline. There is a clear trend towards a decrease in the biotic potential of the Taimyr population at the current rates of reproduction in its migration flows and a further decline in the productivity of the species in that part of the circumpolar distribution range.