Occurrence records of Callistomys pictus.

Knowledge of the potential distribution and locations of poorly known threatened species is crucial for guiding conservation strategies and new field surveys. The painted tree-rat (Callistomys pictus) is a monospecific, rare, and endangered echimyid rodent endemic to the southern Bahia Atlantic Forest in Brazil. There have been no records of the species published in the last 20 years, and the region has experienced significant forest loss and degradation. According to the IUCN, only 13 specimens had been previously reported, with 12 found in the north of Ilhéus and adjacent municipalities, and one recorded approximately 200 km away from this region, suggesting that its distribution might be wider. We aimed to search for unpublished and more recent records of the C. pictus, by consulting the gray literature (including Environmental Impact Study (EIA) reports, Brazilian Red Lists, and management plans of protected areas), scientific collections, online databases, and mastozoologists working in the region. We estimated the species’ potential distribution using Ecological Niche Modeling to identify regions, municipalities, and protected areas most likely to support this species, based on factors such as climate suitability and forest cover. We reported three new sightings of the species, including the first within a protected area. We estimated suitable climate conditions across 23,151 km2, of which 9,225 km2 has a high potential for harboring the species. The area between Itacaré and Valença needs more extensive survey efforts as it has high habitat suitability and only one record has been confirmed there so far. Meanwhile, the region between Una and Ilhéus urgently requires habitat conservation initiatives. While the species may have a broader distribution than previously thought, its known occurrences are limited to a few locations, and suitable habitats are underrepresented in protected areas. Additionally, the rarity of sightings continues to indicate a concerning conservation status.

针对鲜为人知的受威胁物种，掌握其潜在分布范围与具体分布点位，对制定保护策略及开展新的野外调查至关重要。彩树鼠（Callistomys pictus）是单型、稀有且濒危的棘鼠科（Echimyidae）啮齿动物，为巴伊亚州南部大西洋森林的特有物种。该物种已有20年未出现正式发表的观测记录，且其分布区域正经历严重的森林丧失与生境退化。据世界自然保护联盟（International Union for Conservation of Nature, IUCN）记载，此前仅报道过13号标本：其中12号采自伊列乌斯（Ilhéus）北部及周边市镇，另有1号采自距该区域约200公里处，这提示该物种的分布范围可能比此前认知的更广。

本研究旨在通过检索灰色文献（包含环境影响评价（Environmental Impact Study, EIA）报告、巴西红色名录及保护区管理规划）、馆藏标本、在线数据库以及该区域的哺乳动物学家，来搜寻彩树鼠（C. pictus）未正式发表的近期观测记录。本研究基于气候适宜性、森林覆盖度等因子，采用生态位建模法估算该物种的潜在分布范围，以识别最适宜其生存的区域、市镇及保护区。

本次研究共记录到3笔该物种的新观测记录，其中为首例在保护区内的观测记录。经估算，适宜该物种生存的气候覆盖范围达23151平方公里，其中9225平方公里具备极高的物种栖息潜力。伊塔卡雷（Itacaré）与巴伦萨（Valença）之间的区域生境适宜性较高，但截至目前仅确认过一笔观测记录，因此需要开展更全面的调查工作。与此同时，乌纳（Una）与伊列乌斯之间的区域亟需开展生境保护行动。

尽管该物种的分布范围可能比此前认知的更广，但目前已确认的观测点位仍十分有限，且适宜其生存的生境在保护区中的占比偏低。此外，观测记录的稀缺性依然提示该物种的保护现状令人担忧。