Guafo Island Research Articles

New Seal (Carnivora, Phocidae) Record from the Late Miocene–Pliocene of Guafo Island, Southern Chile

Diversos restos de fócidos fósiles (focas) han sido consistentemente reportados en niveles del Mioceno Tardío y Plioceno de América del Sur. Estos fósiles, junto a aquellos de otáridos fósiles (lobos marinos), indican que durante el Plioceno Tardío o Pleistoceno Temprano se produjo un recambio generalizado desde una fauna dominada por fócidos a una dominada por otáridos en el Hemisferio Sur. El registro fósil de fócidos del Neógeno está dominado principalmente por ocurrencias en el sur de Perú y el norte de Chile, con algunos hallazgos aislados en el centro de Chile. Hasta ahora, no se han reportado focas fósiles en el sur de Chile, limitando nuestra comprensión de la variabilidad latitudinal de los ensambles de pinnípedos, así como de los mecanismos por los cuales ocurrió su recambio faunístico. Aquí describimos los restos fósiles de una foca fósil (Monachinae indet.) de los sedimentos del Mioceno Tardío-Plioceno de la Isla Guafo en el sur de Chile. Estos restos constituyen la ocurrencia más austral de una foca fósil en el Océano Pacífico Sur, ampliando su rango de distribución geográfica en la costa sureste de América del Sur en más de 1000 km. Este hallazgo revela que los fócidos habitaron regiones templadas y subantárticas a lo largo de la Patagonia Chilena durante el Neógeno tardío, lo que sugiere una tolerancia ambiental más amplia que la reconocida anteriormente para este grupo.

Genetic diversity and kinship relationships in one of the largest South American fur seal (Arctocephalus australis) populations of the Pacific Ocean

AbstractThe genetic diversity of populations is the basis for individual fitness and potential adaptability to environmental changes. The South American fur seal (Arctocephalus australis) is a pinniped species that is widely distributed along the southern cone of South America. However, two distinct populations have evolved: the Northern Pacific/Peruvian population and the Southern Pacific/Atlantic population. One of the main breeding colonies of the Southern Pacific/Atlantic population is located on Guafo Island, in southern Chilean Patagonia. This breeding colony represents the closest reproductive population to the remote Peruvian group. Therefore, our study aimed to determine whether the Guafo colony may potentially facilitate gene flow, contribute new alleles, and increase genetic variability of the Peruvian populations, thereby linking the Northern and Southern Pacific populations for the species. In this study, species‐specific microsatellite markers were developed to genetically characterize Guafo Island's South American fur seal population. Our results confirm that the Guafo colony is a panmictic population with evidence of lack of genetic structure. Further, our results indicate that most individuals are unrelated and that half‐siblings are rare, suggesting that polygyny in this species is less frequent than previously thought. Finally, based on the identification of multiple pairs of full siblings, we also present the first genetic evidence of twins in South American fur seals. These attributes suggest that the Guafo colony is a large, panmictic population, which could act as a potential genetic reservoir, and ultimately assist in linking two genetically distinct populations.

Towards understanding the effects of oceanic plastic pollution on population growth for a South American fur seal (Arctocephalus australis australis) colony in Chile.

Entanglement of pinnipeds with plastic debris is an emerging conservation and animal welfare issue worldwide. However, the origins and long-term population level consequences of these entanglements are usually unknown. Plastic entanglement could produce a combination of wounds, asphyxiation, or inability to feed that results in the death of a certain percentage of individuals from the total population. In this research, we report on the consequent effect of plastic entanglement on population growth demographics in a South American fur seal (Arctocephalus australis australis) colony on Guafo Island, southern Chile. Using a stochastic matrix population model structured according to age and sex, and assuming an otherwise stable population, we explored population growth rates under five scenarios with differing rates of entanglement: A) a zero rate of plastic entanglement, B) entanglement rates (number of entangled individuals as a proportion of the total number of individuals) as observed in our study population (overall entanglement ratio of 1.2×10-3); and for the other scenarios, entanglement ratios as reported in the literature for other pinniped colonies around the world: C) 3.04×10-3, D) 4.42×10-2, and E) 8.39×10-2. Over the 30 years forecasting period and starting with a population size of ∼2950 individuals, the population growth rate was lower under all scenarios with rates of entanglement greater than zero (scenarios B-E). In comparison with scenario A, at the end of the 30-year period forecasted, we calculated a projected decrease in population size of between 20.34% (scenario B) and 91.38% (scenario E). These results suggest that even the lowest levels of entanglement in pinnipeds as reported in the literature might have significant effects over time on population-level dynamics. Our research offers potential insight when devising policy for the management and limitation of plastic pollution in the oceans, and indeed for the conservation and management policy of affected marine species. Furthermore, whilst there are some limitations to our methodology, it offers a straightforward and potentially useful approach for the standardized prediction of impacts at a population level of different rates of plastic pollution and entanglement and could be applied in distinct populations of the same species around the world.

Connectivity in early life stages of the southern hake, Merluccius australis, in northern Chilean Patagonia

The southern hake, Merluccius australis, is one of the most important marine fishery resources in Chilean Patagonia. However, little is known about its early life history, especially the transport of eggs and larvae and the connectivity between spawning and nursery areas. An individual-based model (IBM) of the early life stages of M. australis, coupled to a hydrodynamic model, was used to track virtual individuals released from known spawning locations and identify potential nursery areas. The simulations were used to assess connectivity and retention of M. australis eggs and yolk-sac larvae within (and between) the continental shelf (offshore) and the inner sea (inshore) zones. The inshore zone included two spawning and nursery areas (Inner Sea of Chiloé (ISCh), Inner Sea of Moraleda Channel ISM)) and the offshore zone included three spawning and nursery areas (Guafo Island, Guamblin Island, and the Taitao Peninsula). The hydrodynamic model was validated using available observations (oceanographic surveys and the World Ocean Atlas 2018) for winter and spring, periods during which M. australis reproductive activity peaks. The IBM reproduced well the observed seasonal variability of egg and larval distributions. Individuals from the offshore spawning areas had low connectivity with those in the inshore nursery areas in winter and spring. However, individuals from the inshore spawning areas showed a high degree of connectivity with one of the offshore nursery areas (Guafo) during winter and spring, but low connectivity between the inshore ones (ISCh and ISM). Guamblin (in winter) and ISCh (in spring) were the most important retention areas. A conceptual model is proposed to represent the connectivity in early developmental stages between the spawning and nursery areas of M. australis: ichthyoplankton is transported from inshore to offshore in winter when little spawning occurs inshore, but not in spring when spawning and retention increases inshore. Retention in the offshore zone in winter is significant, with almost no connectivity with the inshore zone. Since the main spawning of the species occurs in winter in the offshore zone and secondarily in the inshore zone in spring, the seasonal differences in dispersal patterns seem to be part of the reproductive strategy of the species, which apparently confers advantages for the offspring by promoting development in the most advantageous feeding environment for each season (offshore in winter and inshore in spring).

Molecular survey of Bartonella spp. in rodents and fleas from Chile

The aim of this study was to molecularly survey Bartonella spp. in rodents from the Valdivia Province, Southern Chile and from wild black rat-fleas in Guafo Island, Chilean Patagonia. Thrity-three spleens from synanthropic (Mus musculus, Rattus novergicus and Rattus rattus) and wild (Abrothrix longipilis, Oligoryzomys longicaudatus, Abrothrix sp.) rodents from Valdivia and 39 fleas/flea-pools (Plocopsylla sp. and Nosopsyllus sp.) from R. rattus in Guafo Island were obtained. All samples were screened by high-resolution melting (HRM) real-time PCR for Bartonella ITS locus (190 bp). ITS-Positive samples were further analyzed for two HRM real-time PCR assays targeting Bartonella rpoB (191 bp) and gltA (340 bp) gene fragments. All positive ITS, gltA and rpoB real-time PCR products were purified and sequenced. Bayesian inference trees were built for the gltA and rpoB gene fragments. Bartonella-ITS DNA was detected in 36.3% (12/33) [95% CI (22–53%)] of the tested rodents from Valdivia, being identified in all but O. longicaudatus rodent species captured in this study. ITS DNA was detected in 28% (11/39) [95% CI (16-43%)] of fleas/flea-pools from Guafo Island and identified in both Plocopsylla and Nosopsyllus genera. Sequencing and phylogenic analyses targeting three loci of Bartonella spp. allowed the identification of five genotypes in rodents from Southern Chile, potentially belonging to three different Bartonella spp. Those included Bartonella tribocorum identified from R. rattus, Bartonella rochalimae detected from Abrothix sp., and one novel genotype from uncharacterized Bartonella sp. identified in M. musculus, R. norvegicus, A. longipilis, and Abothrix sp., related to strains previously isolated in Phyllotis sp. from Peru. Additionally, two genotypes of B. tribocorum were identified in fleas from Guafo. In a nutshell, highly diverse and potentially zoonotic Bartonella spp. are described for the first time in wild and synanthropic rodents from Chile, and B. tribocorum was detected in wild back rat fleas from Guafo Island.

New non-breeding colonies of the South American fur seal in central Chile. Is the distribution in the southeastern Pacific waters extending?

The South American fur seal (SAFS), Arctocephalus australis, has an estimated abundance of 219,000 individuals. The distribution range of this top marine predator along the Pacifc coast of South America is discontinuous, with a gap between 29°02’S-43°36’S, whereas the Atlantic coast presents a continuous distribution. Little is known aboutthe population dynamics of the species in Chile, as there have been few observations of vagrant individuals within the distribution gap and partial population censuses on dates that do not fit with the reproductive season in northern andsouthern Chile. The aim of this study is to identify the presence of A. australis colonies and summarize the sightings in central Chile. Aerial censuses were performed between 32°12’S-39°24’S during the austral winter and summer (2015) and between 41°44’S-44°55’S during summer (2013, 2016-2018). Official stranding records were also included to complementthe research sightings. We registered a total of 54 SAFS in the Chilean distribution gap, most of them during winter (89%) and with a higher proportion of females (72%). Two non-breeding colonies were found in the Biobío Region during the winter of 2015, Islote del Trabajo (38°25’S) and Islote Quechol (38°26’S), with 27 ± 1 and 16 ± 0 individuals, respectively. The sightings of adult individuals suggest their arrival at these latitudes to carry out foraging and resting activities, probably from Guafo Island (43°36’S). The last Pleistocene glaciation, hunting activities during the eighteenth century and ENSO events could have conditioned the current abundance and range of distribution of A. australis in South America; therefore, the establishment of new non-breeding colonies in the gap of distribution could lead to new breeding grounds in thefuture.

Sighting patterns and habitat use of marine mammals at Guafo Island, Northern Chilean Patagonia during eleven austral summers

The chiloense marine ecoregion, at the Northern Chilean Patagonia, has been considered a hotspot of marine mammal diversity, yet little is known regarding specific sites used by these species for reproduction, nursing, refuge, and foraging. This information is critical for proper spatial ecosystem planning and conservation of marine resources. In the austral summers of 2004 through 2008, and from 2012 to 2017, the presence, distribution, and behavior of 13 species of marine mammals was recorded at Guafo Island, an oceanic island located in the center of the chiloense ecoregion. Guafo Island is an important reproductive and feeding site for South American fur seals (Arctocephalus australis australis), South American sea lions (Otaria byronia) and marine otters (Lontra felina), and an important feeding, nursing, and transit location for humpback whales (Megaptera novaeangliae), Orcas (Orcinus orca), and blue whales (Balaenoptera musculus). We also recorded occasional sightings of fin whales (B. physalus), southern right whales (Eubalaena australis) and Peale’s dolphins (Lagenorhynchus australis). The island coastline also serves as refuge for molting Southern elephant seals (Mirounga leonina) and vagrant Subantarctic fur seals (Arctocephalus tropicalis). The information presented here highlights Guafo Island as an important breeding, shelter, and feeding site for marine mammals in Chile. The growing anthropogenic pressure on this ecosystem emphasizes the importance of formal protection of this island as a priority site for marine conservation in the Northern Patagonia of Chile.

Back to full interseismic plate locking decades after the giant 1960 Chile earthquake

Great megathrust earthquakes arise from the sudden release of energy accumulated during centuries of interseismic plate convergence. The moment deficit (energy available for future earthquakes) is commonly inferred by integrating the rate of interseismic plate locking over the time since the previous great earthquake. But accurate integration requires knowledge of how interseismic plate locking changes decades after earthquakes, measurements not available for most great earthquakes. Here we reconstruct the post-earthquake history of plate locking at Guafo Island, above the seismogenic zone of the giant 1960 (Mw = 9.5) Chile earthquake, through forward modeling of land-level changes inferred from aerial imagery (since 1974) and measured by GPS (since 1994). We find that interseismic locking increased to ~70% in the decade following the 1960 earthquake and then gradually to 100% by 2005. Our findings illustrate the transient evolution of plate locking in Chile, and suggest a similarly complex evolution elsewhere, with implications for the time- and magnitude-dependent probability of future events.

Respiratory Mites ( Orthohalarachne diminuata) and β-hemolytic Streptococci-Associated Bronchopneumonia Outbreak in South American Fur Seal Pups ( Arctocephalus australis).

Although mites of the Orthohalarachne genus are common parasites of otariids, their role as agents of disease and in causing population-level mortality is unknown. In the austral summer of 2016, there was an increase in mortality among South American fur seal ( Arctocephalus australis) pups at Guafo Island, Northern Chilean Patagonia. Pups found dead or terminally ill had moderate to marked, multifocal, mucopurulent bronchopneumonia associated with large numbers of respiratory mites ( Orthohalarachne diminuata) and rare Gram-positive cocci. In lung areas less affected by bronchopneumonia, acute interstitial pneumonia with marked congestion and scant hemorrhage was evident. Bacteria from pups dying of bronchopneumonia were isolated and identified as Streptococcus marimammalium and Streptococcus canis. Respiratory mites obstructed airflow, disrupted airway epithelial lining, and likely facilitated the proliferation of pathogenic β-hemolytic streptococci, leading to severe bronchopneumonia and death of fur seal pups. An abrupt increase in sea surface temperature in Guafo Island corresponded to the timing of the bronchopneumonia outbreak. The potential role of environmental factors in the fur seal pup mortality warrants further study.

Genetic connectivity of the South American fur seal (Arctocephalus australis) across Atlantic and Pacific oceans revealed by mitochondrial genes

Abstract South American fur seals, Arctocephalus australis, were intensively hunted for centuries, leaving the species at the edge of extinction. After the cessation of commercial hunting in the 20th century the overall population has increased to an estimated population of 250 000–300 000 individuals, with Guafo Island being the largest breeding colony in Southern Chile with Guafo Island in Southern Chile being the largest breeding colony. The genetic diversity of the South American fur seal population on Guafo Island and the possible genetic connectivity among populations from the Atlantic and Pacific oceans were studied in order to assess the importance of the Southern Chile Pacific population for the management of the species. Mitochondrial DNA sequences from the Guafo Island population were compared with those from various Atlantic (Brazil, Uruguay, and Argentina) and Pacific (Peru) populations previously studied. The results indicate the occurrence of historical and/or current gene flow among the populations of Guafo Island in the Pacific Ocean and the populations of the Atlantic Ocean, displaying a lack of genetic structure within these areas. In contrast, the Peruvian population is highly divergent compared with the Chilean and Atlantic populations. The lack of genetic structure of Guafo Island fur seals suggests that this group is connected to populations in the Atlantic Ocean. Thus, the significant genetic diversity pool harboured by the Guafo Island population represents the northernmost point of expansion of this species from the Atlantic Ocean to the Pacific Ocean, which could be important for the eventual dispersal of the species to more northern areas of the Pacific and to the future adaptation of the species to changing environmental conditions on the Pacific coasts.

Spatio-temporal variability of ichthyoplankton and its relationship with oceanographic conditions at the shelf break off Chilean Patagonia (43°S–51°S)

ABSTRACTLarval fish composition and abundance have been studied in fjords of south Patagonia. However, the ichthyoplankton of the adjacent shelf and slope waters of the Pacific Ocean, which is an important spawning and nursery ground for demersal fishery species (e.g. austral hake and Patagonian grenadier), remains largely unknown. To compare ichthyoplankton occurrence with environmental conditions in August 2013 and 2014 (austral winter), two bio-oceanographic cruises were carried out between 43° and 51°S. Conductivity, temperature and depth (CTD) data and ichthyoplankton samples were collected. The highest frequency of occurrence (FO) was observed for eggs of lightfish Maurolicus parvipinnis (84 and 91% FO in 2013 and 2014, respectively) and larvae of the myctophid Lampanyctodes hectoris (60 and 94% FO, respectively). Ichthyoplankton composition and abundance varied significantly between years, and richness varied from 10 (2013) to 18 taxa (2014). Only larval L. hectoris showed a significant increase in abundance during the winter of 2014. Water column temperature and salinity were significantly different between years; the water was warmer and saltier in 2013. Canonical Correspondence Analysis detected positive relationships between temperature and salinity with egg abundance and larval distribution of Merluccius australis. The highest abundance of eggs of M. australis was found at ∼6–10°C, mainly off south Guafo Island. Additionally, ichthyoplankton from the shelf-break area off south Patagonia showed a wider latitudinal distribution in the winter of 2014 than in 2013.

Coastal debris survey in a Remote Island of the Chilean Northern Patagonia

Global marine litter pollution is increasing dramatically, and oceanic islands are one of the most vulnerable ecosystems due to their high debris accumulation rate compared to continental sites. Remote areas, such as inhabited islands, represent a perfect study case to track marine debris sources, due to the assumed low rates of local production of debris. Guafo Island is one of the largest islands of the Chilean Northern Patagonia and is considered a remote zone. The accessible coast of Guafo Island was monitored during four austral summers revealing higher levels of marine debris accumulation than continental Chile. Plastic was the most abundant type of debris constituting 50% of the total litter monitored. Our results suggest that most of the plastic identified is likely to be related to local fisheries activities. Mitigation measures including collaboration among fishing communities and scientists could contribute to reduce the coastal debris pollution in remote areas.

Pathological Findings in Wild Rats (Rattus rattus) Captured at Guafo Island, Northern Chilean Patagonia

The black rat (Rattus rattus) is an invasive species and potential reservoir of significant pathogens of man, domestic animals and wildlife. During the 2012-2014 austral summers, 201 black rats were captured and examined on the uninhabited Guafo Island, in Northern Chilean Patagonia (43.593029°S, 74.713481°W). The mite Ornithonyssus bacoti caused lymphoplasmacytic and eosinophilic dermatitis in all infected rats (105/210, 52%), but no skin lesions were observed in rats infected with Nosopsyllus spp. and Plocopsylla spp. fleas. Eighty-eight rats (44%) had mild lymphoplasmacytic and eosinophilic enterocolitis and 61 of these rats were infected with the nematode Heterakis spumosa. In the liver, 63 animals (31%) had areas of necrosis with histiocytic and eosinophilic inflammation associated with multiple Calodium hepaticum eggs, and in 15 cases there was co-infection with several Taenia taeniaeformis strobilocerci. Mild interstitial lymphoplasmacytic sialadenitis with intranuclear inclusion bodies, suggesting cytomegalovirus infection, was observed in 28 rats (15%). In the lung, alveolar histiocytosis (69 rats, 34%) and perivascular lymphocytic infiltrates (46 rats, 23%) were the most common findings. There was mild to moderate lymphoplasmacytic interstitial nephritis in 52 rats (26%) and in 15% of these cases Leptospira spp. antigen was detected in the distal renal tubules. Some of the diseases of black rats on Guafo Island are likely to play a role in rat population dynamics. The endemic Guafo Island long-clawed mole mouse (Geoxus lafkenche), sea lions and fur seals may be at risk for infection by some of these rat pathogens.

Kelp and dolphin gulls cause perineal wounds in South American fur seal pups (Arctocephalus australis) at Guafo Island, Chilean Patagonia.

During five reproductive seasons, we documented the presence, extent and origin of perineal wounds in South American fur seal pups (Arctocephalus australis) on Guafo Island, Northern Chilean Patagonia. The seasonal prevalence of perineal wounds ranged from 5 to 9%, and new cases were more common at the end of the breeding season (February), when pups were on average two months old and were actively expelling hookworms (Uncinaria sp). Histologically, wounds corresponded to marked ulcerative lymphoplasmacytic and histiocytic dermatitis with granulation tissue and mixed bacterial colonies. In 2015 and 2017, kelp gulls (Larus dominicanus) and dolphin gulls (Leucophaeus scoresbii) were observed picking and wounding the perineal area of marked pups. This behaviour occurred more frequently after the pups' defecation, when sea gulls engaged in consumption of pups' faeces. The affected pups usually had moderate to marked hookworm infections along with bloody diarrhoea and anaemia. Pups with severe wounds (23% of affected animals) had swollen perineal areas and signs of secondary systemic bacterial infection. We propose that seagulls on Guafo Island have learned to consume remains of blood and parasites in the faeces of pups affected by hookworm infection, causing perineal wounds during this process. We conclude that this perineal wounding is an unintentional, occasional negative effect of an otherwise commensal gull–fur seal relationship.

Taxonomical notes on the long-clawed mole mice of the genus Geoxus (Cricetidae), with the description of a new species from an oceanic island of southern Chile

The rodent genus Geoxus was largely considered as monotypic; however, a growing body of evidence suggests that this figure is incorrect. In this work, based on qualitative and quantitative morphological evidence and DNA sequence data, we reviewed the alpha taxonomy of this genus. Based on the examination of 134 specimens, four species are recognized within Geoxus : G. annectens (until recently referred to the genus Pearsonomys ), G . michaelseni , G . valdivianus , and one species described herein as new. The four species have unique combinations of qualitative and quantitative morphological characters and were recovered as monophyletic using mitochondrial DNA sequences. The new species diagnosed and named here is endemic of Guafo Island, a small island of 299 square kilometers on southern Pacific Chile. Phylogenetic analysis placed the new species as sister of G. michaelseni , a form widely distributed in southern Argentinean and Chilean Patagonia.

Hematology, Serum Chemistry, and Early Hematologic Changes in Free-Ranging South American Fur Seals ( Arctocephalus australis ) at Guafo Island, Chilean Patagonia.

The establishment of clinical pathology baseline data is critical to evaluate temporal and spatial changes in marine mammal groups. Despite increased availability of studies on hematology and biochemistry of marine mammals, reference ranges are lacking for many populations, especially among fur seal species. During the austral summers of 2014 and 2015, we evaluated basic hematologic and biochemical parameters in clinically healthy, physically restrained South American fur seal ( Arctocephalus australis ) lactating females and 2-mo-old pups. We also assessed the temporal variation of hematology parameters on the pups during their first 2 mo of life. Reference ranges of lactating females were similar to those previously reported in other fur seal species. In the case of pups, reference ranges are similar to values previously reported in sea lion species. As expected, most biochemical and hematologic values differ significantly between adult females and pups. As in other otariids, South American fur seals pups are born with higher values of total red blood cells, hemoglobin, and packed cell volume, and lower numbers of total leukocytes, neutrophils, lymphocytes, and eosinophils. To the best of our knowledge, data on hematology reference values for South American fur seals has not been previously reported and is useful for continued health monitoring of this species, as well as for comparisons with other otariid groups.

Encephalitozoonosis in 2 South American Fur Seal (Arctocephalus australis) Pups

Cerebral and disseminated encephalitozoonosis was diagnosed by histopathology, electron microscopy, and immunohistochemistry in 2 free-ranging South American fur seal pups found dead at Guafo Island (43°33'S 74°49'W) in southern Chile. In the brain, lesions were characterized by random foci of necrosis with large numbers of macrophages containing numerous microsporidial organisms within parasitophorous vacuoles. In addition, occasional histiocytes loaded with numerous mature and immature microsporidia spores consistent with Encephalitozoon sp were observed in pulmonary alveolar septa, splenic red pulp, glomerular capillaries, and proximal renal tubules by Gram and immunohistochemical stains. To our knowledge, microsporidial infection in a marine mammal species has not been previously reported.

Causes of mortality in South American fur seal pups (Arctophoca australis gracilis) at Guafo Island, southern Chile (2004–2008)

AbstractAs part of population dynamics studies of the South American fur seal (Arctophoca australis gracilis) rookery at Punta Weather in Guafo Island (43°36'S, 74°43’W), the causes and extent of pup mortality were monitored. During four breeding seasons, daily counts of live and dead pups were carried out to determine pup production and pup mortality. Dead pups were retrieved from the rookery to perform necropsies. The mean pup production was 1,735.5 ± 336 pups and the mean pup mortality up to 12 wk old was 6.0%± 2.6%. The major causes of death were enteritis with microscopic lesions of bacteremia (28.4%), starvation (23.5%), drowning (21%), trauma (19.8%), and stillbirths (2.5%). Enteritis with microscopic lesions of bacteremia, and starvation had higher incidence during January (beginning and middle of the breeding season) while most trauma and drowning occurred during February (end of the breeding season). In the 2006–2007 breeding season there was an increase in mortality due to starvation and trauma. Most pup deaths at Guafo Island are generated by extrinsic factors; therefore, additional studies that assess the impact of environmental changes and fishing activities, are needed in order to determine the exact causes of the decline of this species along Chilean coasts.

Pathological Findings in South American Fur Seal Pups ( Arctocephalus australis gracilis) found Dead at Guafo Island, Chile

During four breeding seasons (2004-2008), 78 necropsy examinations were performed on South American fur seal pups (Arctocephalus australis gracilis) found dead on Guafo Island, southern Chile (43°36'S, 74°43'W). Tissue samples from 65 pups were examined microscopically. The primary causes of death were enteritis with microscopical lesions of bacteraemia (28.2%), starvation (23.1%), drowning (21.8%), trauma (19.2%) and stillbirth (2.6%). Those pups with enteritis and microscopical lesions of bacteraemia had haemorrhagic enteritis (100%), interstitial pneumonia (86%), periportal hepatitis (73%) and vasculitis (18%). The pups that died from starvation had atrophy of hepatocytes (61%) and cholestasis (61%). The pups that drowned had bronchoalveolar oedema (65%) and foreign bodies in the airways (65%). In animals that died from trauma, the main lesions were skull fractures (67%). This range of pathological findings is within what would be expected in a healthy otariid breeding colony.