Wild ungulates represent one of the most ecologically significant groups in ecosystems, playing a vital role in maintaining ecosystem structure and function. The wild sika deer (Cervus nippon), a first-class nationally protected species in China, is primarily distributed in the central region of the Hunchun Nature Reserve in Jilin Province and the south mountain ranges of the Laoyeling region in Heilongjiang Province. Investigating its spatiotemporal distribution patterns in the southern Laoyeling area in Heilongjiang, one of the core habitats for this species, is fundamental for assessing its ecological value and implementing effective habitat conservation strategies. This study collected information on the activity sites of sika deer in the southern part of Laoyeling, Heilongjiang Province from 2023 to 2024 through far-infrared camera monitoring technology. Single-species single-season occupancy models and kernel density estimation methods were employed to analyze the spatiotemporal distribution characteristics of wild sika deer in this area. The results demonstrated that: (1) The spatial distribution of sika deer was relatively concentrated in Chaoyanggou, Nuanquanhe, Sanchahe, and Yuanshan forest farms, while Zhongguliu and Sanjielizi forest farms had fewer occurrences; (2) The occupancy rate of sika deer in the cold season was 48.34%, with Amur tiger (Panthera tigris altaica), roads, residential areas, altitude, and slope being the significant covariates, each with a weight of 0.50. In the warm season, the occupancy rate of sika deer was 52.94%, with water sources, roads, residential areas, farmlands, altitude, and forest types being the significant covariates, each with a weight of 0.54; (3) Within the distribution range, the activity rhythm curve of sika deer exhibited a “bimodal” pattern, with two daily activity peaks occurring between 6:00—8:00 and 14:00—16:00, although there were seasonal differences. In spring, the activity peaks were delayed and advanced by 2 hours and 3 hours respectively compared to summer. The activity rhythm of sika deer in summer was crepuscular. Both autumn and winter exhibit three daily activity peaks. In autumn, the activity peaks occur at 4:00—6:00, 16:00—18:00, and 21:00—23:00, while in winter, they are observed at 6:00—8:00, 13:00—15:00, and 20:00—22:00. The activity overlap index also indicated that the daily activity peaks of sika deer and Amur tigers were offset. The daily activity peaks of Amur tigers were mainly concentrated in the two time periods of 10:00—12:00 and 22:00—24:00. The activity peaks of Amur leopards primarily occur during two distinct time periods of 5:00—7:00 and 14:00—16:00. The researchers found that although sika deer co-occur with tigers and leopards in the same habitat, there is no significant influence of these large carnivores on deer distribution. However, temporal niche partitioning between the species was observed. These findings provide critical data to support the science-based management of sika deer in Northeast Aumr Tiger and Leopard National Park, while offering empirical evidence for integrated biodiversity conservation strategies tailored to regional ecological characteristics.