Abstract: | Long‐term population studies on large mammals are rare. Here, we have examined the threatened scimitar‐horned oryx, addax and dama gazelle's populations over the last 20 years in Bou Hedma National Park. Using monthly count data of the three studied species collected since 1995, we examined their population trends. Using autocorrelation analyses, we discovered endogenous natural cyclical fluctuations in the numbers of each species, with a periodicity of approximately 3 years. For all three studied species which seem to be opportunistic breeders, births and deaths occurred throughout the year, although with notable seasonality. By means of cross‐correlation, we discovered that during the first 7 years for which data were available, addax numbers were positively correlated with those of dama and inversely correlated with numbers of oryx. This pattern reversed during the following 4‐year period. The number of oryx was negatively correlated with dama during the first 4 years and then became positively correlated during the subsequent 7‐year period. Thus, we draw attention to difference in response to environmental and anthropogenic factors. Incorporating fundamental long‐term population data into developing management approaches, especially for potentially competitive species, is vital for their future long‐term survival and the success of conservation actions. |