Toxoplasmosis in sea lions in NZ

Michael, S. A., Howe, L., Chilvers, B. L., Morel, P. C. H., & Roe, W. D. (2016). Seroprevalence of Toxoplasma gondii in mainland and sub-Antarctic New Zealand sea lion (Phocarctos hookeri) populations. New Zealand Veterinary Journal, (just-accepted), 1-14.

AIMS: To investigate the seroprevalence to Toxoplasma gondii in New Zealand sea lions (Phocarctos hookeri), as a potential contributor to reproductive failure.
METHODS: Archived sera were sourced from New Zealand sea lions from two recolonising mainland populations in the Otago Peninsula (n=15) and Stewart Island (n=12), as well as a declining population at Enderby Island (n=28) in the New Zealand sub-Antarctic. Sera were tested for antibodies to T. gondii using a commercially available ELISA (with samples considered positive if the sample to positive ratio was >30%), and latex agglutination test (LAT; with titres ≥1:32 considered positive). Western blot analysis was used to validate the results of a subset of 14 samples.
RESULTS: Five samples from sea lions in mainland locations were confirmed positive for antibodies to T. gondii. Two adult females exhibited high LAT antibody titres (min 1:2048, max 1:4096) on both occasions when sampled 1 and 2 years apart, respectively. No animals from Enderby Island were seropositive.
CONCLUSIONS: Toxoplasma gondii infection is unlikely to be a major contributor to poor reproductive success in New Zealand sea lions. However, continued surveillance is pertinent to assess subclinical and clinical impacts of the parasite on these threatened populations. The commercial tests evaluated here, with further species-specific threshold refinement could provide a fast, inexpensive and reliable indicator of T. gondii exposure in New Zealand sea lions.

Leptospira in free-living sea lions in California and Baja California

Rosalía Avalos-Téllez, Erika M. Carrillo-Casas, Daniel Atilano-López, Carlos R. Godínez-Reyes, Efrén Díaz-Aparicio, David Ramírez-Delgado, María F. Ramírez-Echenique, Margarita Leyva-Leyva, Gerardo Suzán, and Francisco Suárez-Güemes (2016) Pathogenic Leptospira serovars in free-living sea lions in the gulf of California and along the Baja California coast of Mexico. Journal of Wildlife Diseases In-Press.


The California sea lion (Zalophus californianus), a permanent inhabitant of the Gulf of California in Mexico, is susceptible to pathogenic Leptospira spp. infection, which can result in hepatic and renal damage and may lead to renal failure and death. During summer 2013, we used the microscopic agglutination test (MAT) to investigate the prevalence of anti-Leptospira antibodies in blood of clinically healthy sea lion pups from seven rookery islands on the Pacific Coast of Baja California (Pacific Ocean) and in the Gulf of California. We also used PCR to examine blood for Leptospira DNA. Isolation of Leptospira in liquid media was unsuccessful. We found higher antibody prevalence in sea lions from the rookery islands in the gulf than in those from the Pacific Coast. Antibodies against 11 serovars were identified in the Gulf of California population; the most frequent reactions were against serovars Bataviae (90%), Pyrogenes (86%), Wolffi (86%), Celledoni (71%), and Pomona (65%). In the Pacific Ocean population, MAT was positive against eight serovars, where Wolffi (88%), Pomona (75%), and Bataviae (70%) were the most frequent. Serum samples agglutinated with more than one Leptospira serovar. The maximum titer was 3,200. Each island had a different serology profile, and islands combined showed a distinct profile for each region. We detected pathogenic Leptospira DNA in 63% of blood samples, but we found no saprophytic Leptospira. Positive PCR results were obtained in blood samples with high and low MAT titers. Together, these two methods enhance the diagnosis and interpretation of sea lion leptospirosis. Our results may be related to human activities or the presence of other reservoirs with which sea lions interact, and they may also be related to sea lion stranding.

Ecology of the feral cat on Macquarie Island

Jones, E. (1977). Ecology of the feral cat, Felis catus (L.),(Carnivora: Felidae) on Macquarie Island. Wildlife Research, 4(3), 249-262.

On Macquarie Island from December 1973 to March 1975 the diet of feral domestic cats (Felis catus) was estimated. There was rabbit (Oryctolagus cuniculus) in 82% of faeces and 71% of guts, rabbits under 600 g bodyweight, about 10 weeks old, were 81% of all rabbits eaten. There were Antarctic prion (Pachyptila desolata) and white-headed petrel (Pterodroma lessonii). Cats ate small numbers of rats, mice and wekas and scavenged on dead elephant seals and penguins, especially in winter. Availability of food in winter seemed to be an important factor limiting the population; adult population was estimated to be 250 to 500 and the area of the island is 120 km². Prion and white-headed petrel nest in burrows; there was little or no predation by cats on surface nesters such as albatross, giant petrel, southern skua or southern black-backed gull, or on live penguin.

Feral dogs as potential threat for pinnipeds

García-Aguilar, M.C. & J.P. Gallo-Reynoso 2012. Feral dogs at Isla de Cedros, Baja California, Mexico: a possible threat for pinnipeds. . Revista Mexicana de Biodiversidad, 83 (3): 785-789.

The presence of feral dogs (Canis lupus familiaris) in Isla de Cedros, Baja California, Mexico, has been documented for over 15 years. In the summer of 2009 and the winter of 2009/2010, 2 sampling surveys were conducted in the northeast coastal portion of the island to assess the diet of feral dogs in the vicinity of hauled out California sea lions (Zalophus californianus) and northern elephant seals (Mirounga angustirostris). Mammals were the most important prey group in the diet of dogs (85.4%). Our results show that in the northeast coast of Isla de Cedros, feral dogs feed on pinnipeds: the elephant seal was the most important prey in both seasons (43.3% in summer and 51.9% in winter), followed by the sea lion as the second most important prey during the summer (23.3%), while its importance decreased in the winter (5.8%). Besides the potential predatory activity, there is an important likelihood that pinnipeds could be infected by pathogens of dogs, with serious epizootic consequences.


García-Aguilar, M.C. & J.P. Gallo-Reynoso 2012. Perros ferales en la isla de Cedros, Baja California, México: una posible amenaza para los pinnípedos. Revista Mexicana de Biodiversidad, 83 (3): 785-789.

La presencia de perros ferales (Canis lupus familiaris) en la isla de Cedros, Baja California, México, fue documentada hace más de 15 años. En el verano de 2009 e invierno 2009/2010, se realizaron 2 campañas de muestreo en la costa noreste de la isla para evaluar los hábitos alimentarios de los perros en las cercanías de las zonas de reproducción y descanso del lobo marino de California (Zalophus californianus) y del elefante marino del norte (Mirounga angustirostris). Los mamíferos constituyeron el grupo consumido más importante en la alimentación de los perros (85.4%). Los resultados de este estudio muestran que en la costa noreste de la isla de Cedros los perros se alimentan de pinnípedos: el elefante marino fue la especie que más se consumió, con el mayor porcentaje en ambas temporadas (43.3% en verano y 51.9% en invierno); el lobo marino, fue la segunda durante el verano (23.3%), aunque su porcentaje disminuyó en el invierno (5.8%). Además del potencial impacto que el consumo por los perros pueda tener sobre las poblaciones de los pinnípedos, una amenaza adicional es la posible transmisión de los patógenos caninos, con serias consecuencias epizoóticas.

Monitoring feral dog’s population at Isla de Cedros

García-Aguilar, M.C. 2012. Monitoring feral dog’s population at Isla de Cedros, Baja California, and the associated threats over native mastofauna. Acta Zoológica Mexicana (n. s.), 28(1): 37-48.

Monitoring introduced species is an important management tool in order to preserve native species. The aim of this study was to monitor the feral dog’s population in Isla de Cedros and to identify actual and potential threats of their presence over the native mastofauna. Data were collected at two sampling areas of the island, the Northeast Coast (CNE) and the Central-South Region (RCS). Dog’s distribution pattern and density was assess using a non-invasive method based on scat counts along transect surveys and relative density (R) and faecal relative abundance index (fRAI) were estimated. Dog’s diet composition was evaluated by scat analysis. Both R and fRAI were significant greater (P < 0.05) in the CNE than in the RCS. The results showed that feral dogs are feeding from at least three endemic terrestrial mammal species (the mule deer, the brush rabbit, and the Anthony’s pocket mouse) and two pinnipeds species (the northern elephant seal and the California sea lion). With this study provide a useful baseline for future comparison and monitoring and control purposes. Nevertheless, it is necessary to conduct studies about the dog’s feeding behavior to measure their predatory activity and to assess the associated damage level. Also, due to the fact that interactions between dogs and pinnipeds appeared frequently and because they are phylogenetically related, the greatest threat of the dog’s presence is that it could be a disease vector, with serious health outcomes for the wildlife.


García-Aguilar, M. C. 2012. Monitoreo de la población de perros ferales en la Isla de Cedros, Baja California, y las amenazas a la mastofauna nativa. Acta Zoológica Mexicana (n. s.), 28(1): 37-48.

El monitoreo de especies introducidas es una herramienta importante para preservar las especies nativas. El objetivo de este estudio fue monitorear a la población de perros ferales en la Isla de Cedros e identificar las amenazas actuales y potenciales de su presencia sobre la mastofauna nativa. La colecta de datos se realizó en dos áreas de la isla, la costa noreste (CNE) y la región centro-sur (RCS). Los patrones de distribución y la densidad de los perros se determinaron con un método no invasivo basado en el conteo de excretas a lo largo de transectos y se estimó la densidad relativa (R) y el índice de abundancia relativa fecal (fRAI). La composición de la dieta se evaluó por medio del análisis de las excretas. Tanto los valores de R como de fRAI fueron significativamente mayores (P < 0.05) en CNE que en RCS. Los resultados mostraron que los perros se alimentan de al menos tres especies de mamíferos endémicos (el venado bura, el conejo matorralero y el ratón de abazones de Cedros) y de dos especies de pinnípedos (el elefante marino del norte y el lobo marino de California). A partir de este estudio se cuenta con una línea de base que podrá ser usada en los programas de control y monitoreo futuros. Sin embargo, es necesario desarrollar estudios sobre el comportamiento alimentario de los perros para evaluar su actividad predatoria y medir el nivel de daño asociado; además, dado que las interacciones entre pinnípedos y perros parecen ser frecuentes y están relacionados filogenéticamente, posiblemente la mayor amenaza de la presencia de los perros sea la propagación de enfermedades infeccionas, con graves resultados para la vida silvestre.

Eradication and control of feral dogs in Galápagos

Barnett, B. D. (1986). Eradication and control of feral and free-ranging dogs in the Galápagos Islands. In Proceedings of the Twelfth Vertebrate Pest Conference (1986) (8 pp.).

The history of canid introduction in Galápagos, their impact on biodiversity and the control and eradication by different methods, mainly poisoning with 1080 and chemical sterilisation.

After eradication in some areas, some mesopredator release effect was detected and cats further threatened iguanas populations. Sea lions became free of this danger, but cattle invaded areas previously occupied by dogs.

Dog outcompete vultures at sea lion colony

Pavés, H. J., Schlatter, R. P., & Espinoza, C. I. (2008). Scavenging and predation by Black Vultures Coragyps atratus at a South American sea lion breeding colony. Vulture News, 58(1), 4-15.

Many animal species benefit from resources provided by other species. Such species may develop or coevolve particular interspecific relationships (for example: competition, depredation and mutualism). During two sea lion breeding seasons (1996-97 and 1997- 98), we observed behavioral interactions at the Punta Lobería Southern Sea-lion Otaria flavescens colony. We documented facultative mutualism, commensalism and depredation by Black Vulture Coragyps atratus, Kelp Gull Larus dominicanus and Domestic Dogs Canis familiaris on sea lions. Competitive relationships between Black Vulture and dogs were observed. We recorded depredatory behaviour by vultures on live seal pups. Black Vultures were the dominant bird consumer on carcasses in the absence of feral dogs. Sea lion mother displayed agonistically when Black Vultures approached their pups. Vultures fed on sea lion placentas and umbilical cords during the birth period. 12-17% of the sea lion pups suffered attacks by Black Vultures during our two season's observations. Dogs compete advantageously with vultures on seal pup carcasses. We postulate that the shift
from mutualistic scavenging to depredation by vultures may be influenced by hunger stress due to competition with feral dogs for limited sea lion carrion.


Distintas especies de animales se asocian y benefician de los recursos generados en una colonia reproductiva de lobo marino común (Otaria flavescens), desarrollando un conjunto de relaciones interespecíficas coevolutivas particulares (competencia, depredación, mutualismo, entre otros). Durante dos periodos reproductivos (1996-1997 y 1997-1998) se realizaron observaciones de las conductas interespecíficas en la colonia reproductiva de Punta Lobería (38º39'S; 73º29'W). Se registraron relaciones de tipo mutualista, comensal y depredadoras, entre Jote cabeza negra (Coragyps atratus), Gaviota dominicana (Larus dominicanus) y Perros domésticos abandonados (Canis familiaris) sobre O. flavescens. Relaciones competitivas entre Jote cabeza negra, Jote de cabeza colorada (Cathartes aura), Gaviotas dominicanas y perros domésticos fueron también identificadas. Los Jotes en ausencia de perros vagos tienden a ser los carroñeros dominantes en este tipo de gremio. Las madres de los cachorros de lobo marino común despliegan conductas agonísticas ante la aproximación de jotes quienes se alimentan de las placentas y cordones umbilicales expulsados durante el parto. Se registraron conductas de tipo depredadora de jotes sobre cachorros vivos de lobo marino común. Entre un 12% y 17% de los cachorros sufrieron ataques por jotes durante ambas temporadas. Los perros vagos compiten en forma ventajosa con jotes por carroña. Se postula que la redirección de una conducta carroñera mutualista a depredadora, en el jote de cabeza negra, estaría influenciada por estrés alimentario, bajo el efecto competitivo dominante con perros vagos por cadáveres de lobos marinos.

Cats milking seals!!!

Juan-Pablo Gallo-Reynoso, J.P. & C. L. Ortiz. 2010. Feral cats steal milk from northern Elephant Seals. THERYA, 1(3): 207-212

Feral cats abound at Isla de Guadalupe; they forage on birds, mice, and placental tissue as well as carcasses of northern elephant seals (Mirounga angustirostris), Guadalupe fur seal (Arctocephalus townsendi), California sea lions (Zalophus californianus) and stranded cetaceans such as Cuvier’s beaked whale (Ziphius cavirostris). We have found that feral cats are also drinking elephant seal’s milk, stealing it directly from the teats of nursing females. The amount of energy obtained this way might be significant for feral cats in the northern elephant seal rookeries on the island.