Inventory of Wildlife-Associated Nests, Burrows, Refuges, and Cavities – San Juan National Historic Site (SJNHS)
Naveira Guzman M, Sepulveda Mangual A, Pietri C, Diaz Mendez L. 2026. Inventory of Wildlife-Associated Nests, Burrows, Refuges, and Cavities – San Juan National Historic Site (SJNHS). National Park Service - Cultural Resources - Wildlife Program. San Juan National Historic Site - SAJU. https://doi.org/10.36967/2319171
This report presents a comprehensive and georeferenced inventory of nests, burrows, refuges, and cavities used by native, endemic, migratory, and introduced wildlife within the San Juan National Historic Site (SJNHS), with particular emphasis on microhabitats associated with the invasive green iguana (Iguana iguana). Conducted between August and December 2025, the study followed a standardized monitoring protocol that included systematic transects, GPS and Survey123 data collection, photographic documentation, and qualitative field notes. A total of 556 structures were recorded, consisting of 478 herbages, 66 caves, and 12 burrows, with the highest concentrations found at Castillo San Felipe del Morro, Baluarte de Santa Elena, and Batería San Fernando. The active occupancy rate was 15.6%, revealing a marked disconnect between structure availability and actual use, influenced by environmental factors such as microclimate, vegetation, substrate conditions, coastal erosion, and human activity. More than 95% of all documented structures were located within or directly associated with historic architectural elements—including walls, bastions, drainage systems, and fortifications—highlighting the significant dependence of wildlife, including invasive species, on cultural resources. Qualitative observations further noted extensive use of drainage systems, wall cavities, erosional voids, and vegetation-rooted microhabitats by iguanas, land crabs, feral cats, pigeons, and bees, underscoring the ecological complexity embedded within the park’s historical infrastructure. Statistical analyses, including descriptive metrics, heatmaps, density maps, and a run test, indicated that the spatial distribution of structures is essentially random, while a Pareto analysis showed that approximately 30% of zones account for more than 70% of all structures, identifying clear management priorities. In alignment with NEPA, NPS Management Policies, ESA considerations, and USFWS mitigation guidelines, the report emphasizes the need for balanced and adaptive management strategies that protect both cultural resources and native biodiversity while addressing the threats posed by invasive species. The study provides a robust baseline for future monitoring, habitat restoration, invasive species control, and interdisciplinary conservation planning, reinforcing the importance of data-driven decision-making for safeguarding the ecological and historical integrity of the SJNHS.
- Type
- Published Report
- Authors
- Naveira Guzman, Miguel; Sepulveda Mangual, Adriana; Pietri, Carlos; Diaz Mendez, Luanna
- Date of Issue
- 2026-03-14
- Publisher
- National Park Service - Cultural Resources - Wildlife Program
- DOI
- 10.36967/2319171
- Units
- SAJU
- Keywords
- Active occupation rate, ArcGIS, Burrows, Castillo San Cristóba, Castillo San Felipe del Morro, Cavities, control Ecological restoration, Counting, Cultural Resources, Endemic Species, Exotic Species, Georeferencing, Green iguana, Historic Site, Historic structures use by invasive species, Iguana iguana, Invasive Species, Inventory, l Invasive species, Management, Microhabitats, Native Species, Natural Resources, nests, Puerto Rico, Refuges, Risk‑prediction, SAJU, SER, SJNHS, Southeast, Spatial distribution, spatial independence, Survey123, Systematic monitoring, Wildlife structures
- Subjects
- Ecological Framework: Biological Integrity | Invasive Species | Invasive/Exotic animals , Ecological Framework: Biological Integrity | Focal Species or Communities | Amphibians and Reptiles
- License
- Public Domain