Understanding and being able to predict the relationship between animal population growth and their environment has been an interesting aspect in animal ecology. Following the major decline in elephant population the Nyerere ecosystem in between 2009 and 2014 (TAWIRI, 2015) the government of Tanzania stepped in to curb poaching. The elephant population is monitored using regular aerial survey every three years but also monitoring the population structure to gate an indication of how the population is recovering. Population structure derived from demographic parameters such as herd size, age group, cow/calf ratio, breeding adult ratio, young adult ratio and female-male ratio of the population. These are critical information for the growth of any population. Elephant age will be assigned in age classes (0-4, 5-9, 10-14, 15-19, 20-24, 25-39 and 40+ (Poole, 1989; Moss 1996). A group of elephants is defined as any number of elephants of any age or sex moving together in a coordinated manner with no single member or sub-group at a distance greater than the diameter of the main body of the group. Cow/Calf group defined as any group containing one or more adult females. Males over 10 years old were not included in the group size. Individuals below 5 years old are considered as calves. Calves under 1 years of age are considered as new infants. All individuals < 10 years old will be considered as dependents. All females over 10 years old are considered as mothers. All cow-calf groups seen together with bulls are defined as mixed groups. A bull group contained only of males above 10 years old while an aggregation in this regard are all groups of elephants with more than twenty individuals with more than one family unit with or without adult males and the single adult males are considered as lone bulls.

Predicting the future population trends is important for conservation and ecosystem management. The distribution of the population structure can be used as an index to infer the trend and history of the population. In a growing elephant population with increasing human population and expansion of human settlement, Human-Elephant Conflict (HEC) is inevitable. Understanding the population demography will be crucial to predict the future trend and devise an appropriate management strategy including protection of the species especially at this time when poaching is high. Again, it is demonstrated that female elephants that are released from poaching tends to reduce birth interval and also early pregnancy for the first-time female (Owens & Owens, 2009).

Updating elephant population structure and distribution in the Nyerere-Selous Ecosystem