Species conservation and management require reliable information about animal distribution and population size. Better management actions within a species' range can be achieved by identifying the location and timing of population changes. In the Greater Mahale Ecosystem (GME), western Tanzania, deforestation due to the expansion of human settlements and agriculture, annual burning, and logging are known threats to wildlife. For one of the most charismatic species, the endangered eastern chimpanzee (Pan troglodytes schweinfurthii), approximately 75% of the individuals are distributed outside national park boundaries, requiring monitoring and protection efforts over a vast landscape of various protection statuses. These efforts are especially challenging when we lack data on trends in density and population size. To predict spatio-temporal chimpanzee density and abundance across the GME, we used density surface modeling, fitting a generalized additive model to a 10-year time-series data set of nest counts based on line-transect surveys. The chimpanzee population declined at an annual rate of 2.41%, including declines of 1.72% in riparian forests (from this point forward, forests), 2.05% in miombo woodlands (from this point forward, woodlands) and 3.45% in nonforests. These population declines were accompanied by ecosystem-wide declines in vegetation types of 1.36% and 0.32% per year for forests and woodlands, respectively; we estimated an annual increase of 1.35% for nonforests. Our model predicted the highest chimpanzee density in forests (0.86 chimpanzees/km², 95% confidence intervals (CIs) 0.60–1.23; as of 2020), followed by woodlands (0.19, 95% CI 0.12–0.30) and nonforests (0.18, 95% CI 0.10–1.33). Although forests represent only 6% of the landscape, they support nearly one-quarter of the chimpanzee population (769 chimpanzees, 95% CI 536–1103). Woodlands dominate the landscape (71%) and therefore support more than a half of the chimpanzee population (2294; 95% CI 1420–3707). The remaining quarter of the landscape is represented by nonforests and supports another quarter of the chimpanzee population (750; 95% CI 408–1381). Given the pressures on the remaining suitable habitat in Tanzania, and the need of chimpanzees to access both forest and woodland vegetation to survive, we urge future management actions to increase resources and expand the efforts to protect critical forest and woodland habitat and promote strategies and policies that more effectively prevent irreversible losses. We suggest that regular monitoring programs implement a systematic random design to effectively inform and allocate conservation actions and facilitate interannual comparisons for trend monitoring, measuring conservation success, and guiding adaptive management.

中文翻译：

---

坦桑尼亚大马哈勒生态系统中黑猩猩密度和丰度的时空变化

物种保护和管理需要有关动物分布和种群规模的可靠信息。通过确定种群变化的位置和时间，可以在一个物种的范围内采取更好的管理行动。在坦桑尼亚西部的大马哈勒生态系统 (GME)，人类住区和农业扩张导致的森林砍伐、每年的焚烧和伐木是对野生动物的已知威胁。对于最具魅力的物种之一，濒临灭绝的东部黑猩猩（Pan troglodytes schweinfurthii), 大约 75% 的个体分布在国家公园边界之外, 需要对各种保护状态的广阔景观进行监测和保护工作。当我们缺乏关于密度和人口规模趋势的数据时，这些努力尤其具有挑战性。为了预测整个 GME 的时空黑猩猩密度和丰度，我们使用密度表面建模，将广义加性模型拟合到基于线横断面调查的 10 年时间序列巢数数据集。黑猩猩种群以每年 2.41% 的速度下降，其中河岸森林（从此时起，森林）下降 1.72%，miombo 林地（从此时起，林地）下降 2.05%，非森林下降 3.45%。这些人口减少伴随着生态系统范围内植被类型的减少 1.36% 和 0。森林和林地每年分别减少 32%；我们估计非林业的年增长率为 1.35%。我们的模型预测了森林中黑猩猩的最高密度（0.86 只黑猩猩/km^2个, 95% 置信区间 (CI) 0.60–1.23；截至 2020 年），其次是林地（0.19，95% CI 0.12–0.30）和非森林（0.18，95% CI 0.10–1.33）。尽管森林仅占景观的 6%，但它们养育了将近四分之一的黑猩猩种群（769 只黑猩猩，95% CI 536–1103）。林地在景观中占主导地位 (71%)，因此养育了一半以上的黑猩猩种群 (2294；95% CI 1420–3707)。其余四分之一的景观以非森林为代表，并支持另外四分之一的黑猩猩种群（750；95% CI 408–1381）。鉴于坦桑尼亚剩余适宜栖息地的压力，以及黑猩猩需要进入森林和林地植被才能生存，我们敦促未来的管理行动增加资源并扩大保护重要森林和林地栖息地的努力，并促进更有效地防止不可逆转损失的战略和政策。我们建议定期监测计划实施系统随机设计，以有效告知和分配保护行动，并促进趋势监测、衡量保护成功和指导适应性管理的年度间比较。