Captive Breeding Facility Research Articles

Polymorphic DNA microsatellite markers for forensic individual identification and parentage analyses of seven threatened species of parrots (family Psittacidae).

The parrot family represents one of the bird group with the largest number of endangered species, as a result of habitat destruction and illegal trade. This illicit traffic involves the smuggling of eggs and animals, and the laundering through captive breeding facilities of wild-caught animals. Despite the huge potential of wildlife DNA forensics to determine with conclusive evidence illegal trade, current usage of DNA profiling approaches in parrots has been limited by the lack of suitable molecular markers specifically developed for the focal species and by low cross-species polymorphism. In this study, we isolated DNA microsatellite markers in seven parrot species threatened with extinction (Amazona brasiliensis, A. oratrix, A. pretrei, A. rhodocorytha, Anodorhynchus leari, Ara rubrogenys and Primolius couloni). From an enriched genomic library followed by 454 pyrosequencing, we characterized a total of 106 polymorphic microsatellite markers (mostly tetranucleotides) in the seven species and tested them across an average number of 19 individuals per species. The mean number of alleles per species and across loci varied from 6.4 to 8.3, with the mean observed heterozygosities ranging from 0.65 to 0.84. Identity and parentage exclusion probabilities were highly discriminatory. The high variability displayed by these microsatellite loci demonstrates their potential utility to perform individual genotyping and parentage analyses, in order to develop a DNA testing framework to determine illegal traffic in these threatened species.

Fertility suppression of some wildlife species in southern Africa—a review

Generally speaking, southern Africa's wildlife populations in small-to-medium-sized protected game reserves (10,000-65,000ha) reproduce at rapid rates which often lead overpopulation of certain species. Most commonly these are large predators such as lions, African wild dogs and cheetahs, and elephants. Overpopulation of large predators leads to depletion of prey species, breakouts into neighbouring communities and increased risks for disease transmission. An overabundance of elephants leads to habitat destruction which is to the detriment of not only other herbivores but also certain bird species. By far, the most acceptable and effective method of population control is contraception. Another problem, particularly in South Africa, is the large numbers of large predators that are held in zoos, wildlife sanctuaries or captive breeding facilities. Once again, there is a need for contraception to control the rate of reproduction. In this review, we discuss the methods that have been most commonly used for some wildlife species in southern Africa. The methods include hormonal control and immunocontraception. We also address the problem of androgen-related aggressive behaviours in elephant bulls and giraffe males and present solutions that have been used to ameliorate such behaviours.

Intraerythrocytic rickettsial inclusions in endangered Kaiser’s mountain newt, Neurergus kaiseri (Caudata: Salamandridae)

ABSTRACTPathogens of different kinds may infect amphibians at various stages of their life and can be the immediate causes of their mortality. Salamanders are hosts to a variety of parasites, including intracellular bacteria in the order Rickettsiales. All bacteria in this order are obligate, intracellular (usually within erythrocytes) organisms that are transmitted by arthropod vectors. By examining stained blood smears of Neurergus kaiseri under a light microscope, we encountered single or multiple round, clear to faint purple with dark purple ring inclusions within the cytoplasm which were similar to intraerythrocytic rickettsial inclusion bodies. Reported here is a case of the rickettsial-like inclusions in N. kaiseri in a captive breeding facility for the first time in Iran.

Composition of the Cutaneous Bacterial Community in Japanese Amphibians: Effects of Captivity, Host Species, and Body Region.

The cutaneous microbiota plays a significant role in the biology of their vertebrate hosts, and its composition is known to be influenced both by host and environment, with captive conditions often altering alpha diversity. Here, we compare the cutaneous bacterial communities of 61 amphibians (both wild and captive) from Hiroshima, Japan, using high-throughput amplicon sequencing of a segment of the 16S rRNA gene. The majority of these samples came from a captive breeding facility at Hiroshima University where specimens from six species are maintained under highly standardized conditions for several generations. This allowed to identify host effects on the bacterial communities under near identical environmental conditions in captivity. We found the structure of the cutaneous bacterial community significantly differing between wild and captive individuals of newts, Cynops pyrrhogaster, with a higher alpha diversity found in the wild individuals. Community structure also showed distinct patterns when comparing different species of amphibians kept under highly similar conditions, revealing an intrinsic host effect. Bacterial communities of dorsal vs. ventral skin surfaces did not significantly differ in most species, but a trend of higher alpha diversity on the ventral surface was found in Oriental fire-bellied toads, Bombina orientalis. This study confirms the cutaneous microbiota of amphibians as a highly dynamic system influenced by a complex interplay of numerous factors.

Individual Identification of the Endangered Wyoming ToadAnaxyrus baxteriand Implications for Monitoring Species Recovery

Abstract Monitoring the fates of individuals after release in the wild is essential for building effective species recovery programs. Current conservation efforts for the endangered Wyoming Toad (Anaxyrus baxteri) are limited by the size and number of toads that can be individually marked using invasive tagging techniques. We evaluated the use of natural patterns of wart-like glands on the dorsum of Wyoming Toads as a potential identification technique. We photographed 194 known-identity individuals (822 total images, representing 1,554 true matching-image pairs of the same individuals) from two captive-breeding facilities in 2011 and 2012. Spot patterns provided stable markings from metamorphosis through adult life stages, and naive observers correctly matched 100% of a subset of photo pairs “by eye.” In contrast, computer-assisted identification performed relatively poorly: the two software platforms tested (Wild-ID and Hotspotter) failed to match 47% and 64% of true matching-image pairs, respectively. ...

Genetic evidence for multiple paternity in the critically endangered Cuban crocodile (Crocodylus rhombifer)

Conservation strategies can be most effective when factors influencing the persistence of populations are well-understood, including aspects of reproductive biology such as mating system. Crocodylians have been traditionally associated with a polygynous mating system, with genetic studies revealing multiple paternity of clutches in several species. The endemic Cuban crocodile,Crocodylus rhombifer, is currently listed as Critically Endangered, and is one of the least understood crocodylian species in terms of its mating behavior. Here, we tested a hypothesis of multiple paternity in the Cuban crocodile by collecting genotypic data at nine microsatellite loci for 102 hatchlings from five nests sampled at the Zapata Swamp captive breeding facility and analyzing them in relation to data previously collected for 137 putative parents. All five nests showed evidence of multiple paternity based on the numbers of alleles per locus, with sibship analyses reconstructing all nests as having four to six full-sib family groups. Accordingly, mean pairwise relatedness values per nest ranged from 0.21 to 0.39, largely intermediate between theoretical expected values for half-siblings (0.25) and full-siblings (0.50). It is not possible to differentiate whether the multiple paternity of a nest was due to multiple matings during the same breeding season, or a result of sperm storage. Our results reveal that theC. rhombifermating system is likely best characterized as promiscuous and suggest that the standard practice of enforcing a 1:2 sex ratio at the captive breeding facility should be altered in order to better maintain a demographically and genetically healthy ex situ population.

Avian Polyomavirus Genome Sequences Recovered from Parrots in Captive Breeding Facilities in Poland.

Eight genomes of avian polyomaviruses (APVs) were recovered and sequenced from deceased Psittacula eupatria, Psittacula krameri, and Melopsittacus undulatus from various breeding facilities in Poland. Of these APV-positive samples, six had previously tested positive for beak and feather disease virus (BFDV) and/or parrot hepatitis B virus (PHBV).

Detecting the nesting suitability of the re-introduced Crested Ibis Nipponia nippon for nature restoration program in Japan

The Crested Ibis, became extinct in the wild in Japan in 1981; however, a captive breeding facility was established on Sado Island, Niigata Prefecture in 1999 in the hope of conserving the species. Following successful breeding at the facility, a group of birds was released on Sado Island on 25th September 2008, with further reintroductions in subsequent years. Habitat restoration is also necessary to facilitate the re-introduction program of this endangered species. The aim of this study was to detect suitable nesting areas for the released ibises on Sado Island for subsequent nature restoration. Since little ibis nesting information was available for Sado Island, the nesting model was constructed from nesting information from China, from which results were extrapolated for Sado Island. Land usage was assessed using LANDSAT/ETM+ data for China and SPOT/HRG images for Sado Island. In this study, land-use information was used to define the environmental parameters related to nest site selection of the Crested Ibis. For the nesting model, a generalized linear mixed model, with seven environmental factors, was employed. The multi-spatial scale for Crested Ibis nesting was also analyzed. We took the spatial scale into consideration at intervals of 100m from a buffer size of 100m to 2500m. Because nest site selection was influenced by the results of the previous year, nesting location data in 2005 and 2006 were distinguished and models built accordingly. Several important environmental factors were identified for nest site selection: the ratio of broadleaved deciduous forest to coniferous forest; the shape of the forest edge; and, the distance from rice fields and other wetlands. The model’s accuracy was verified using the Boyce index, and shows the validity of the model’s results. Suitable nesting areas for the Crested Ibis were found mainly on: the Kuninaka plain; the ridgeline between the Kuninaka plain and the Osado or Kosado mountain ranges; the area around Lake Kamo; and, the midwestern area of the Kosado region. Suitable nesting sites for the Crested Ibis were all found to be concentrated in what is known as Yatsuda, a traditional Japanese landscape structure providing a complex mosaic of forest and rice fields with complex ecotones. Eastern Kosado, the region that has been designated by the Ministry of the Environment as the conservation area for the reintroduced birds, was not judged to provide suitable nesting habitat for the Crested Ibis. Unfortunately, no evaluation of habitat suitability was made prior to the release of the first captive-bred Crested Ibis into the wild on Sado Island. Had an evaluation of habitat suitability been performed prior to release, more effective nature restoration could have been planned.

Batrachochytrium dendrobatidis detected in Kihansi spray toads at a captive breeding facility (Kihansi, Tanzania).

The chytrid fungus Batrachochytrium dendrobatidis (Bd) is the aetiological agent of amphibian chytridiomycosis, a disease associated with global amphibian population declines. In November 2012, mass mortalities of Kihansi spray toads Nectophrynoides asperginis were observed at the Kihansi captive breeding facility, located in the Udzungwa Mountains, Tanzania. Mortalities increased rapidly, and dead toads showed typical clinical signs of chytridiomycosis, including reddening of the skin that was especially evident on the toe pads. Treatment of toads with itraconazole rapidly reduced mortalities. Dead toads (n = 49) were collected and used to perform Bd-specific polymerase chain reaction and subsequent nucleotide sequencing. All toads collected at the facility were positive for Bd. The obtained Bd 5.8S rRNA gene and flanking internal transcribed spacer regions (ITS1 and ITS2) were not 100% identical to any other Bd sequences in GenBank, but closely resembled isolates from Ecuador, Japan, USA, Brazil, Korea, and South Africa. To our knowledge, this is the first study reporting molecular characteristics of Bd isolated from the Udzungwa Mountains. Strict biosecurity measures at the breeding facility and in Kihansi spray wetlands where toads have been reintroduced have been implemented. Further studies on Bd epidemiology in the Udzungwa Mountains are recommended in order to understand its origin, prevalence, and molecular characteristics in wild amphibian populations. This will be important for conservation of several endemic amphibian species in the Udzungwa Mountains, which are part of the Eastern Arc Mountains, a global biodiversity hotspot.

Population structure and genetic signs of population bottlenecks in the endangered Hawaiian tree snail Achatinella sowerbyana

The native Hawaiian tree snail Achatinella sowerbyana has, along with its remaining congeners, experienced drastic population reductions in the past century. The species is endemic to O’ahu, and currently persists in fragmented wild populations and in a captive breeding facility at the University of Hawai’i at Manoa. We used seven microsatellite loci to examine genetic diversity and population structure, to look for genetic effects of population reductions, and to estimate current effective population sizes of four sampling locations on O’ahu, Hawai’i. We also sought to test the genetic similarity of the captive snails to the wild samples. Our results show low levels of inbreeding, but relatively low levels of genetic diversity. Bottleneck tests identified bottlenecks at each of the four populations, and current effective population sizes ranged from 9 to 68, indicating that continued reductions in genetic diversity are likely due to drift. There was measurable structure among populations, including significant FST values between all sampling locations, and two main clusters, each containing two populations. Attempts to assign the captive bred individuals to wild populations indicated they were more closely related to the southern populations, but that they were divergent from any of the wild populations. Our results indicate that, although introduced predators and habitat fragmentation still threaten A. sowerbyana, genetic concerns must also be addressed in managing this species. Strategies that retain the highest amount of genetic diversity and that are mindful of the population structure detected will provide A. sowerbyana the best chance for persistence.

Fecal microbiota and antibiotic resistance in ferrets (Mustela putorius furo) from two captive breeding facilities in Italy

The microbiota of the intestinal tract plays important roles in the overall health, productivity and well-being of the animals. We have characterized the intestinal microbiota of the ferret because its human cohabitation may increase the possibility of new zoonosis. The presence of anaerobic and microaerophilic bacteria has been evaluated in fresh fecal specimens of 40 ferrets in apparently good health. The bacteria most frequently isolated were Clostridium acetobutylicum (25/40 samples, 62.5%; 95% confidence interval [CI]: 45.81–76.83%) and Helicobacter spp. (16/40 samples, 40.0%; 95% CI: 25.28–56.61%), as anaerobic and microaerophilic bacteria, respectively. The Kirby–Bauer disc-diffusion method showed penicillin, streptomycin and vancomycin resistances in high percentages (>80%) of the bacterial isolates, both in anaerobic and microaerophilic groups. Furthermore, the microaerophilic-bacteria group exhibited a significantly higher antibiotic-resistance profile compared to that of anaerobic-bacteria group. The presence of antibiotic-resistant microorganisms in the microbiota of the ferret gastrointestinal tract is a great concern for public health.

Status of the Santa Catalina Island Fox Thirteen Years after Its Decline

Santa Catalina Island was home to an estimated 1342 adult island foxes (Urocyon littoralis catalinae) in 1990. Nine years later, fox sightings declined and reports of dead or dying foxes increased. An island-wide trapping effort was initiated after a fox carcass tested positive for Canine distemper virus (CDV). In 1999, only 10 foxes were captured east of the Two Harbors isthmus during 1046 trap-nights. A multifaceted conservation plan was implemented in 2000 to conserve the Santa Catalina population of island fox. Initial recovery actions took place from 2000 to 2005 and resulted in the translocation of 22 juvenile foxes from the unaffected West End of the island to the depopulated eastern portion, the production and release of 37 pups from the captive breeding facility, and the vaccination of >80% of the wild fox population against CDV. Since 2006, fox recovery activities have included an annual island-wide population survey, vaccination of 300 foxes per year, weekly mortality monitoring of 50 radio-collared individuals, blood sampling to monitor the prevalence of CDV, veterinary treatment of injured foxes, and public outreach. Low mortality rates, successful breeding in the wild, and mitigation of the original cause of decline allowed for Catalina's fox population to grow to an estimated 1115 adults by 2012 and to be considered biologically recovered. The outbreak of another virulent canine disease on Santa Catalina Island, such as CDV or rabies, continues to be the greatest threat to the long-term survival of U. l. catalinae due to the species' restricted distribution and small population size, as well as the continued presence of domestic dogs on the island.

Familial aggregation of chronic diarrhea disease (CDD) in rhesus macaques (Macaca mulatta)

Chronic diarrheal disease (CDD) is a critical problem for breeders of captive rhesus macaque (Macaca mulatta), as it results in significant levels of morbidity and death annually. As with other inflammatory disorders, CDD is thought to be caused by environmental and/or genetic factors. Although correspondence between the characters defined as Mendelian by pedigree or segregation analysis and functional genes is difficult to establish, such analyses provide essential entry points into understanding CDD in captive bred rhesus macaques. To investigate the familial aggregation of CDD in captive rhesus macaque, we performed pedigree, segregation and heritability analyses on genealogical data from 55 severely affected individuals (probands) through whom relatives with a history of CDD were ascertained from routine computerized colony records comprising vital and demographic statistics of 10,814 rhesus macaques. We identified 175 rhesus macaques with CDD and estimated its incidence as approximately 2% in the colony. The disease strongly clustered in eight multi-generation pedigrees. Inspection of the pedigrees, segregation analysis and heritability estimate of CDD suggest that susceptibility to the disease is under strong genetic control. Identification of the locations of susceptibility genes in the rhesus macaque genome could facilitate the reduction of their frequency in captive breeding facilities.

Extensive recombination detected among beak and feather disease virus isolates from breeding facilities in Poland

Beak and feather disease virus (BFDV) causes the highly contagious, in some cases fatal, psittacine beak and feather disease in parrots. The European continent has no native parrots, yet in the past has been one of the world's biggest importers of wild-caught exotic parrot species. Following the banning of this practice in 2007, the demand for exotic pet parrots has largely been met by established European breeding facilities, which can also supply buyers outside Europe. However, the years of unregulated importation have provided numerous opportunities for BFDV to enter Europe, meaning the likelihood of birds within captive breeding facilities being BFDV positive is high. This study examined the BFDV status of such facilities in Poland, a country previously shown to have BFDV among captive birds. A total of 209 birds from over 50 captive breeding facilities across Poland were tested, and 43 birds from 18 different facilities tested positive for BFDV. The full BFDV genomes from these 43 positive birds were determined, and phylogenetic analysis revealed that these samples harboured a relatively high degree of diversity and that they were highly recombinant. It is evident that there have been multiple introductions of BFDV into Poland over a long period of time, and the close association of different species of birds in the captive environment has probably facilitated the evolution of new BFDV strains through recombination.

China’s Captive Tigers: An Application of the Precautionary Principle to Policy

Tigers have been subject to large and prolonged declines in the wild for several reasons, including poaching. Policies to arrest this decline have been ongoing but marked by failure. One controversial element of the management of tigers is the large captive-breeding facilities in China. This controversy stems from uncertainties about the consequences of these facilities and the best policies to pursue. These uncertainties motivate the employment of the precautionary principle in this research. The precautionary principle is appropriate given the high levels of uncertainty associated with tiger conservation. The precautionary principle is intended to avoid irreversible biodiversity losses. This means the primary concern is the likelihood of different strategies leading to a decline in wild tiger numbers rather than the potential for an increase. This paper applies the precautionary principle to three policy options. These options are to; first, close the facilities down; second, continuing to maintain a large captive population; and third, to resume It is argued that the precautionary principle favours maintaining a high captive population to forestall a consumer switch to black-market sources. Given that this situation is not sustainable, research to resolve some important information gaps is imperative.

392 Basal-phenotypes in breast carcinoma – morphological, immunohistochemical and clinical analysis

The Crested Ibis, became extinct in the wild in Japan in 1981; however, a captive breeding facility was established on Sado Island, Niigata Prefecture in 1999 in the hope of conserving the species. Following successful breeding at the facility, a group of birds was released on Sado Island on 25th September 2008, with further reintroductions in subsequent years. Habitat restoration is also necessary to facilitate the re-introduction program of this endangered species. The aim of this study was to detect suitable nesting areas for the released ibises on Sado Island for subsequent nature restoration. Since little ibis nesting information was available for Sado Island, the nesting model was constructed from nesting information from China, from which results were extrapolated for Sado Island. Land usage was assessed using LANDSAT/ETM+ data for China and SPOT/HRG images for Sado Island. In this study, land-use information was used to define the environmental parameters related to nest site selection of the Crested Ibis. For the nesting model, a generalized linear mixed model, with seven environmental factors, was employed. The multi-spatial scale for Crested Ibis nesting was also analyzed. We took the spatial scale into consideration at intervals of 100 m from a buffer size of 100 m to 2500 m. Because nest site selection was influenced by the results of the previous year, nesting location data in 2005 and 2006 were distinguished and models built accordingly. Several important environmental factors were identified for nest site selection: the ratio of broadleaved deciduous forest to coniferous forest; the shape of the forest edge; and, the distance from rice fields and other wetlands. The model’s accuracy was verified using the Boyce index, and shows the validity of the model’s results. Suitable nesting areas for the Crested Ibis were found mainly on: the Kuninaka plain; the ridgeline between the Kuninaka plain and the Osado or Kosado mountain ranges; the area around Lake Kamo; and, the midwestern area of the Kosado region. Suitable nesting sites for the Crested Ibis were all found to be concentrated in what is known as Yatsuda, a traditional Japanese landscape structure providing a complex mosaic of forest and rice fields with complex ecotones. Eastern Kosado, the region that has been designated by the Ministry of the Environment as the conservation area for the reintroduced birds, was not judged to provide suitable nesting habitat for the Crested Ibis. Unfortunately, no evaluation of habitat suitability was made prior to the release of the first captive-bred Crested Ibis into the wild on Sado Island. Had an evaluation of habitat suitability been performed prior to release, more effective nature restoration could have been planned.

Behavioral Changes, Stress, and Survival Following Reintroduction of Persian Fallow Deer from Two Breeding Facilities

Reintroductions often rely on captive-raised, naïve animals that have not been exposed to the various threats present in natural environments. Wild animals entering new areas are timid and invest much time and effort in antipredator behavior. On the other hand, captive animals reared in predator-free conditions and in close proximity to humans may initially lack this tendency, but can reacquire some antipredator behavior over time. We monitored the changes in antipredator-related behaviors of 16 radio-collared Persian fallow deer (Dama mesopotamica) reintroduced to the Soreq Valley in Israel from 2 breeding facilities: one heavily visited by the public (The Biblical Zoo of Jerusalem, Israel) and the other with reduced human presence (Hai-Bar Carmel, Israel). We monitored each individual for up to 200 days after release, focusing on flush and flight distance, flight mode (running or walking), and use of cover. In addition, we compared fecal corticosterone (a stress-related hormone) from samples collected from known animals in the wild to samples collected in the breeding facilities. Reintroduced individuals from both origins exhibit increased flush distance over time; flush and flight distances were larger in individuals from Hai-Bar; use of cover increased with time, but was greater in Hai-Bar Carmel animals; corticosterone levels were significantly higher in fecal samples from reintroduced animals than in samples from captive animals; and Hai-Bar Carmel animals had an 80% survival rate over the 200 days, whereas no animals from the Biblical Zoo of Jerusalem survived. Reintroduced Persian fallow deer reacquired antipredator behaviors after the release, but the process was slow (months) and differences between conditions at the breeding facilities that were seemingly benign (e.g., number of visitors and other human related activities) influenced this process and consequently affected the success of the reintroduction. Captive breeding facilities for the purpose of reintroduction should minimize anthropogenic disturbances.

Monitoring reproduction in the critically endangered marsupial, Gilbert’s potoroo ( Potorous gilbertii): Preliminary analysis of faecal oestradiol-17β, cortisol and progestagens

Gilbert’s potoroo ( Potorous gilbertii) was rediscovered in 1994 after having been presumed extinct for 120 years. Estimates indicate fewer than 40 individuals remain at Two Peoples Bay Nature Reserve on the south coast of Western Australia although a translocated population of approximately 20 animals has recently been established on nearby Bald Island. A captive breeding facility has been established adjacent to the mainland population but few young have been produced (8 since 1995). Faecal levels of oestradiol-17β (E 2) were monitored over a 2-year period in an effort to determine cyclic reproductive activity, and faecal cortisol levels were also monitored to gauge whether chronic stress may be a factor limiting breeding in captivity. Faecal steroids were monitored in six captive females, and four captive male potoroos, and four wild females. The only captive births recorded after 1998 were one in August 1999 and one in February 2001, both to the same female. Peaks in E 2 concentration, up to 10 ng g −1 of dried faecal mass were measured and results to date suggest the main breeding period to be November–December based on elevated E 2 levels at this time. Clear patterns of reproductive activity in the captive females, however, were not evident. Analysis of epithelial cell counts from urinogenital swabs and faecal E 2 and progestagen (PM) levels from a single female kept at the Perth Zoo, suggest that Gilbert’s potoroo has an oestrous cycle of approximately 39 days. Faecal cortisol levels in captive females were significantly lower than those in wild-caught individuals and thus there is no indication that elevated cortisol levels per se inhibited reproduction in captive females.

Reintroduction Failure of Captive-Bred Oribi (Ourebia ourebi)

Oribi (Ourebia ourebi) are listed as endangered and one of the options to increase their numbers and populations is to breed them in captivity and subsequently reintroduce them into suitable habitat. A captive breeding facility for oribi in KwaZulu-Natal, South Africa, had been used to reintroduce captive-bred oribi on to the neighbouring agricultural/game farm for the previous 10 years. However, the success of these reintroductions was unknown. Consequently the aim of this study was to monitor the success of the reintroduction of captive-bred oribi. As in previous years, 10 captive-bred oribi were released by the owners of the facility onto the neighbouring farm. Using radio-telemetry and mortality sensors, survivorship of the reintroduced oribi was monitored, and the factors involved in a successful or failed reintroduction attempt Identified. Within two months of release, seven of the 10 oribi were dead. The causes of mortality varied, but predation by natural predators and humans was a major factor. C...

Rodent malaria-resistant strains of the mosquito, Anopheles gambiae, have slower population growth than -susceptible strains

BackgroundTrade-offs between anti-parasite defence mechanisms and other life history traits limit the evolution of host resistance to parasites and have important implications for understanding diseases such as malaria. Mosquitoes have not evolved complete resistance to malaria parasites and one hypothesis is that anti-malaria defence mechanisms are costly.ResultsWe used matrix population models to compare the population growth rates among lines of Anopheles gambiae that had been selected for resistance or high susceptibility to the rodent malaria parasite, Plasmodium yoelii nigeriensis. The population growth rate of the resistant line was significantly lower than that of the highly susceptible and the unselected control lines, regardless of whether mosquitoes were infected with Plasmodium or not. The lower population growth of malaria-resistant mosquitoes was caused by reduced post blood-feeding survival of females and poor egg hatching.ConclusionWith respect to eradicating malaria, the strategy of releasing Plasmodium-resistant Anopheles mosquitoes is unlikely to be successful if the costs of Plasmodium-resistance in the field are as great as the ones measured in this study. High densities of malaria-resistant mosquitoes would have to be maintained by continuous release from captive breeding facilities.