Turkalo Andrea K, Wrege Peter H, Wittemyer George
The Wildlife Conservation Society, B.P., Bangui, Central African Republic.
The Elephant Listening Project, Bioacoustics Research Program, Cornell Lab of Ornithology, Ithaca, New York, United States of America.
PLoS One. 2018 Feb 15;13(2):e0192777. doi: 10.1371/journal.pone.0192777. eCollection 2018.
African forest elephants face severe threats from illegal killing for ivory and bushmeat and habitat conversion. Due to their cryptic nature and inaccessible range, little information on the biology of this species has been collected despite its iconic status. Compiling individual based monitoring data collected over 20 years from the Dzanga Bai population in Central African Republic, we summarize sex and age specific survivorship and female age specific fecundity for a cohort of 1625 individually identified elephants. Annual mortality (average = 3.5%) and natality (average = 5.3%) were lower and markedly less variable relative to rates reported for savanna elephant populations. New individuals consistently entered the study system, leading to a 2.5% average annual increase in the registered population. Calf sex ratios among known birth did not differ from parity. A weak seasonal signal in births was detected suggesting increased conceptions during the wet season. Inter-calf intervals and age of primiparity were longer relative to savanna elephant populations. Within the population, females between the ages of 25-39 demonstrated the shortest inter-calf intervals and highest fecundity, and previous calf sex had no influence on the interval. Calf survivorship was high (97%) the first two years after birth and did not differ by sex. Male and female survival began to differ by the age of 13 years, and males demonstrated significantly lower survival relative to females by the age of 20. It is suspected these differences are driven by human selection for ivory. Forest elephants were found to have one of the longest generation times recorded for any species at 31 years. These data provide fundamental understanding of forest elephant demography, providing baseline data for projecting population status and trends.
非洲森林象面临着来自非法猎杀获取象牙和食用丛林肉以及栖息地转变的严重威胁。由于它们隐秘的习性和难以进入的活动范围，尽管该物种具有标志性地位，但关于其生物学的信息收集得很少。通过汇总从20多年来在中非共和国的Dzanga Bai象群收集的基于个体的监测数据，我们总结了1625头个体识别大象群体的性别和年龄特异性存活率以及雌性年龄特异性繁殖力。与报道的草原象种群的比率相比，年死亡率（平均 = 3.5%）和出生率（平均 = 5.3%）较低且明显变化较小。新个体不断进入研究系统，导致登记种群平均每年增长2.5%。已知出生的幼崽性别比例与胎次无关。检测到出生存在微弱的季节性信号，表明雨季受孕增加。与草原象种群相比，产犊间隔和初产年龄更长。在种群中，25 - 39岁的雌性产犊间隔最短且繁殖力最高，并且之前的幼崽性别对间隔没有影响。幼崽出生后头两年的存活率很高（97%），且不存在性别差异。雄性和雌性的生存率在13岁时开始出现差异，到20岁时，雄性的生存率明显低于雌性。据推测，这些差异是由人类对象牙的选择导致的。森林象被发现是所有物种中记录的世代时间最长的之一，为31年。这些数据提供了对森林象种群统计学的基本理解，为预测种群状况和趋势提供了基线数据。
