Key Biodiversity Area Secretariat, BirdLife International, Cambridge, UK.
Wildlife Conservation Society, Bronx, New York, USA.
Am J Primatol. 2021 Jul;83(7):e23288. doi: 10.1002/ajp.23288. Epub 2021 May 31.
Grauer's gorillas (Gorilla beringei graueri) have declined drastically across their range in eastern Democratic Republic of Congo (DRC). Survey data analysed in 2016 estimated a 77% decline in numbers between the mid- 1990s and 2016 and predicted that Kahuzi-Biega National Park (KBNP), and the contiguous Oku Community Reserve (OCR) held much of the global population. An estimate of 3800 Grauer's gorillas was made across its range at that time. Here, we publish the most extensive survey of Grauer's gorilla numbers to date, using nest counts from 230 line transects across KBNP and OCR to derive more accurate estimates of both gorilla and chimpanzee numbers. Gorilla numbers were estimated from line transects at 1,571 (95% confidence interval [CI]: 824-2,993) within KBNP and at 2,244 (95% CI: 1,471-3,422) in OCR. Eastern chimpanzee (Pan troglodytes schweinfurthii) numbers were estimated at 2,500 (95% CI: 1,804-3,462) in KBNP and 687 (95% CI: 472-999) in OCR. Estimates of total numbers for the survey area were 5,252 (95% CI: 3,687-7,481) Grauer's gorillas and 4,275 (95% CI: 3,322-5,502) eastern chimpanzees. Chimpanzee numbers were not significantly different from the estimates in the mid-1990s but the gorillas had significantly declined, mostly in KBNP. Modeled densities of these apes indicated that distances to mines, villages, or roads significantly explained part of the distribution of these apes, with higher densities also found in more rugged and remote sites. Other primates have all declined in this region, likely due to bushmeat hunting, especially the Endangered Ulindi River Red Colobus Piliocolobus lulindicus. These results confirm the negative impact of insecurity on Grauer's gorilla but indicate that the population declines may not be as great as previously feared. Using our revised gorilla density estimate we revise the original estimate of global numbers from 3,800 to 6,800 individuals.
格雷氏大猩猩（Gorilla beringei graueri）在其分布范围内的数量在刚果民主共和国（DRC）东部急剧下降。2016 年分析的调查数据估计，1990 年代中期至 2016 年间，数量减少了 77%，并预测卡胡兹-别加国家公园（KBNP）和毗邻的奥库社区保护区（OCR）拥有全球大部分人口。当时，对其分布范围内的格雷氏大猩猩数量的估计为 3800 只。在这里，我们发表了迄今为止对格雷氏大猩猩数量的最广泛调查，使用了来自 KBNP 和 OCR 的 230 条线路样带的巢数来更准确地估计大猩猩和黑猩猩的数量。通过线路样带对 KBNP 内的 1571 只（95%置信区间[CI]：824-2993）和 OCR 内的 2244 只（95%CI：1471-3422）大猩猩数量进行了估计。在 KBNP 内估计的东部黑猩猩（Pan troglodytes schweinfurthii）数量为 2500 只（95%CI：1804-3462），在 OCR 内为 687 只（95%CI：472-999）。调查区域的总数估计为格雷氏大猩猩 5252 只（95%CI：3687-7481）和东部黑猩猩 4275 只（95%CI：3322-5502）。黑猩猩的数量与 20 世纪 90 年代中期的估计没有显著差异，但大猩猩的数量明显下降，主要是在 KBNP。这些猿类的模型密度表明，到矿山、村庄或道路的距离显著解释了这些猿类的部分分布，在更崎岖和偏远的地方也发现了更高的密度。该地区的其他灵长类动物数量都有所下降，可能是由于狩猎野味，尤其是濒危的 Ulindi 河红疣猴 Piliocolobus lulindicus。这些结果证实了不安全对格雷氏大猩猩的负面影响，但表明种群数量的下降可能没有之前担心的那么大。利用我们修正后的大猩猩密度估计值，我们将全球数量的原始估计值从 3800 只修正为 6800 只。
