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Estimating the postmortem interval (PMI) in cetaceans is challenging. These mammals often sink after death, later floating and traveling considerable distances before stranding, complicating decomposition stage analysis. Our study investigates decomposition patterns in humpback whale, guiana dolphin, and franciscana dolphin. We analyzed decomposition stages using photographic data from Instituto Baleia Jubarte (IBJ) and conducted a controlled guiana dolphin carcass decomposition study in a laboratory to establish a reliable PMI baseline for carcasses found along Brazil's Abrolhos Bank region. Our findings reveal species-specific decomposition timelines: humpback whale carcasses typically beach within 14 days post-death maximum, while franciscana and guiana dolphins strand within seven to eight days. The most common PMI for whales was five to six days, guiana dolphins four days, and franciscana dolphins four to five days. We used the five decomposition codes: I alive animals, II fresh carcass, III moderate decomposition, IV advanced decomposition, V skeletal remains. For small cetaceans, code II indicates a PMI of two days, III four days, and IV seven days. For large whales, code II signifies a PMI of one day, III three days, and IV seven days. PMI estimation is vital for identifying the period a carcass floated from death site to shoreline. This information supports forensic approaches in understanding anthropogenic impacts on cetacean mortality and aids ecological and conservation studies regarding cetacean strandings, using PMI and backtracking techniques.

Ocean currents, driven by gravity, wind, and water density, disperse marine biota worldwide, often leading species to shorelines alive or as carcasses. These carcasses provide vital information about species' health conditions and threats within their habitats. Marine animal strandings thus offer crucial insights into the ecological implications of population mortality. This research is instrumental for conservation efforts and identifying trends and threats. Scientists use human and animal forensics approaches to trace the origins of beached bodies. The capability to backtrack carcass drift and estimate death sites helps evaluate anthropogenic impacts. This information also forms the basis for legal applications and gives ecological indicators for marine megafauna conservation. Using backtracking in forensic ecology for conservation research presents expansive investigative opportunities. This paper offers a comprehensive review of: 1) Physical and environmental processes; 2) Drift applications; 3) Marine megafauna examples; 4) Forensic principles; 5) Postmortem intervals; 6) Marine megafauna backtracking. We further discuss these findings' potential conservation applications for endangered species. Our review aims to enhance understanding of coastal animal distribution, estimate mortality rates from strandings, explore seasonal variations for beach monitoring programs, and investigate anthropogenic impacts.

This study describes the pathologic findings of 24 humpback whales (Megaptera novaeangliae) found stranded along the Brazilian coast from 2004 to 2016. Eighteen (75%) animals evaluated were found stranded alive. From these, 13 died naturally on shore and five were euthanized. Six died at sea and were washed ashore. Of the 24, 19 (79.2%) were calves, four (16.7%) were juveniles, and one (4.2%) was an adult. The most probable cause of stranding and/or death (CSD) was determined in 23/24 (95.8%) individuals. In calves, CSD included neonatal respiratory distress (13/19; 68.4%), infectious disease (septicemia, omphaloarteritis and urachocystitis; 3/19; 15.8%), trauma of unknown origin (2/19; 10.5%), and vehicular trauma (vessel strike; 1/19; 5.3%). In juveniles and adult individuals, CSD was: emaciation (2/5; 40%), sunlight-thermal burn shock (1/5; 20%); and discospondylitis (1/5; 20%). In one juvenile, the CSD was undetermined (1/5; 20%). This study integrates novel findings and published case reports to delineate the pathology of a South-western Atlantic population of humpback whales. This foundation will aid in the assessment of the population health and establish a baseline for development of conservation policies.