Use of black rhino range estimates for conservation decisions: a response to Linklater et al.

Abstract

References E M S L I E , R.H. (1999) The feeding ecology of the black rhinoceros (Diceros bicornis minor) in Hluhluwe-Umfolozi Park, with special reference to the probably causes of the Hluhluwe population crash.

Standardising Home Range Studies for Improved Management of the Critically Endangered Black Rhinoceros

“…Although, as predicted, our range size estimates were smaller than those reported previously [ 8 , 47 ], we expected their use of small amounts of location data spread across multiple years [ 3 , 25 ], to result in a much larger home range inflation. It may be that we have underestimated the degree of home range inflation because our bivariate KUD home range estimates are also somewhat inflated by spatial error from our triangulations which contribute to about 50% of our animal locations.…”

“…It is more likely, therefore, that the numbers of locations Reid et al [ 8 ] used are so small (as few as 10) that they under-estimated multi-year range sizes but, nevertheless, approximated rhinos’ smaller annual home range sizes. Indeed, when Slotow et al [ 47 ] re-analysed the same 11-year data set as Reid et al [ 8 ] using rhino (n = 19) that had a sufficient number of locations (i.e., ≥ 50), average range sizes became 68% larger than our estimate (i.e., 20.4 km 2 cf. 34.3 km 2 ).…”

“…The historical sequence of home range size estimates for black rhino in HiP have been used to conclude that their habitat is deteriorating and the reserve over-populated because home ranges sizes have increased [ 8 , 47 ]. But comparing KUD home ranges, constructed with a small number of locations collected fortuitously over many years, with more rudimentary home range procedures (e.g., 1-km 2 grid-cell occupancy and MCPs) from data collected over shorter periods, is another explanation for the apparent increase [ 3 ].…”

“…Others have found similar discrepancies between home range procedures [ 4 ]. Black rhino home ranges derived using KUDs cannot be legitimately compared with more rudimentary techniques like MCPs or 1-km 2 grid-cell occupancy in the way they have been (e.g., [ 8 ], [ 47 ]; see Table 1 and Fig 6 ).…”

“…To allow comparison with other historical estimates of black rhino home ranges in HiP [ 8 , 45 – 47 ], we applied Hitchin’s [ 45 – 46 ] technique (a subjective smoothed line drawn around the outer-most locations), 95% MCP’s, and 50% and 95% KUD contours calculated using a smoothing parameter (h) of 500 m and a cell size of 100 m to our data ( Fig 1 ).…”