Cavia Aperea Research Articles

Photoperiodic effects on reproductive development in male cavies (Cavia aperea)

Age at maturity is a particularly important life history parameter, as it predicts potential life time reproductive success in many small mammal species. Animals should therefore optimize the timing of maturation by reacting to environmental stimuli that predict future environmental conditions. Photoperiod often reliably predicts ecological conditions. Animals born into a photoperiod indicating favorable conditions (spring, summer) may mature earlier and at a lower weight than animals born into conditions indicating unfavorable conditions (autumn, winter). So far most work was done on small, altricial rodent species and we still lack knowledge about their precocial relatives. Precocial animals are born much further developed than altricials and might show less plasticity in their ontogenetic trajectory than the latter.We tested the influence of photoperiod simulated by increasing (spring) or decreasing (autumn) light in climate chambers on important life history parameters in a medium sized rodent, the highly precocial cavy (Cavia aperea). We wanted to determine whether photoperiod influences timing of maturation and early growth in male cavies and whether patterns of testosterone in blood are reflected by patterns of testosterone metabolites in feces.Males born into simulated spring grew faster and matured at an earlier age than males born into simulated autumn conditions. Patterns of testosterone in blood correlated with testosterone metabolites measured in feces. Male cavies strongly react to predictive photoperiod cues by adjusting growth and timing of maturation as we found previously for females, corroborating the importance of seasonal cues for adjustments of life history.

Taphonomic Analysis of Micromammal Remains from Striped Owl (Pseudoscops clamator) Pellets in Northeastern Buenos Aires Province, Argentina: Implications for Archaeological Sites Formation

AbstractThe main objective of this study was to determine the taxonomic and taphonomic characteristics of the micromammal remains recovered from pellets of Pseudoscops clamator (striped owl), collected at three localities in northeastern Buenos Aires Province, Argentina (Punta Lara Natural Reserve, 34°49'02,6''S, 58°03'03,9''W; Costanera Sur Ecological Reserve, 34°36'6,44" S, 58°21'33,22" W; Los Robles Park, 34°40'22,03''S, 58°52'18,88''W). The main taphonomic variables (e.g. evidence of digestive action, breakage patterns and relative abundance of skeletal elements) suggest that this owl mainly produces intermediate to moderate modification. On the other hand, P. clamator preyed mainly upon large‐sized (>150 g) micromammals (e.g. Lutreolina crassicaudata, Cavia aperea, Holochilus brasiliensis and Rattus sp.), and to a lesser degree on medium‐ (50–150 g) and small‐sized species (<50 g) (e.g. Scapteromys aquaticus, Calomys sp., Oligoryzomys flavescens, Akodon azarae and Mus musculus). Fossil assemblages with a dominance of large‐sized micromammals are commonly associated with humans as agents of accumulation. However, this study demonstrates that this owl produces assemblages with abundant large‐sized micromammals, which introduces an equifinality problem. In that sense, digestive corrosion marks, breakage patterns and the relative abundance of skeletal remains are the main attributes to differentiate P. clamator from humans, as agents of accumulation. Finally, our results might serve as an analytical model for the taphonomic interpretation of the fossil record of micromammals from paleontological and archaeological sites, which fall within the distributional range and habitat of P. clamator. Copyright © 2013 John Wiley & Sons, Ltd.

New findings on the origin of Cavia intermedia, one of the world's rarest mammals

AbstractCavia intermedia, a rare species of cavy found exclusively on Moleques do Sul Island, Brazil, differs from other cavies in genetic and morphological characteristics and has been regarded as phylogenetically closest to Cavia magna. Here, I present morphological evidence for the likely origin of Cavia intermedia from an ancestor shared with Cavia magna: an external female genital organ similar in size and appearance to the male's penis. Masculinization of the female genitalia has been observed in Cavia magna but does not occur in Cavia aperea, which suggests a sister relationship between Cavia magna and Cavia intermedia.

Molecular characterization of virulent Leptospira interrogans serogroup Icterohaemorrhagiae isolated from Cavia aperea

Leptospirosis is a worldwide zoonotic infection caused by pathogenic Leptospira. Synanthropic rodents are recognized carriers of leptospires; however, the role of wild rodents in the epidemiology of the disease is still incipient. In this work, we describe Leptospira strain isolated from Cavia aperea (Brazilian guinea pig). The isolated strain was characterized by partial rpoB gene sequencing, variable-number tandem-repeats and histopathological analysis. The strain was identified as Leptospira interrogans, serogroup Icterohaemorrhagiae and caused clinical signs of leptospirosis in the hamster model, attesting to its virulence. In conclusion, these findings could be useful for elucidating the epidemiological role of C. aperea in leptospirosis.

Mating behaviour in wild guinea pigs (Cavia aperea) in captivity

Mating behaviour in wild guinea pigs (Cavia aperea) in captivity

Effects of chronic stress during pregnancy on maternal performance in the guinea pig (Cavia aperea f. porcellus)

Stress experienced during pregnancy can have persistent impact on the female's physiology and behaviour not only during but even beyond pregnancy. The present study aimed to evaluate such long-term effects of stress in terms of repeated strobe light exposure during early to mid gestation on behavioural aspects of mothering activities and lactational effort in lactating guinea pigs. We found that maternal behaviour was negatively affected by stress experience during pregnancy with treatment females developing a higher level of offspring-directed aggression than controls. In addition, our measure of lactational performances showed tendencies of lowered milk supply and longer pup suckling durations in stressed females. We suggest that this may represent a strategy to advance infant weaning following demanding conditions caused by chronic stress experience during pregnancy.

Photoperiod influences the behavioral and physiological phenotype during ontogeny

Behavioral, physiological, and life-history traits can be modified through interactions with environmental conditions during ontogeny. Until recently, the ecological and social circumstances influencing the developing phenotype have not been investigated in much detail. Nevertheless, they represent an important step in niche construction by which the developing organism can in principle adjust to predictable aspects of its life history. By dynamically changing photoperiod during gestation, we tested how behavioral phenotypes (BPs) and physiology of juvenile cavies (Cavia aperea) adjust to seasonal differences in prenatal photoperiod. The prenatal photoperiod, simulating spring or autumn, led to faster or slower maturation in females but the relative size rank in litter also exerted a major influence on the onset of maturation. In addition, prenatal photoperiod strongly influenced BP and stress response in juvenile animals. Heavy females born into autumn developed a less explorative, more shy BP, whereas heavy females born into spring produced more explorative, bolder BP. Smaller sisters did not differ in the onset of maturation and, correspondingly, we found no differences in the BP. We did not find differences in the BP in males also. Early personality traits, though repeatable, changed over ontogeny to such an extent that early group differences in BP had completely disappeared in adults. Our results indicate high developmental plasticity with respect to predicted optimal life history and suggest long-term plasticity in response to photoperiod.

A comparison of brain gene expression levels in domesticated and wild animals.

Domestication has led to similar changes in morphology and behavior in several animal species, raising the question whether similarities between different domestication events also exist at the molecular level. We used mRNA sequencing to analyze genome-wide gene expression patterns in brain frontal cortex in three pairs of domesticated and wild species (dogs and wolves, pigs and wild boars, and domesticated and wild rabbits). We compared the expression differences with those between domesticated guinea pigs and a distant wild relative (Cavia aperea) as well as between two lines of rats selected for tameness or aggression towards humans. There were few gene expression differences between domesticated and wild dogs, pigs, and rabbits (30–75 genes (less than 1%) of expressed genes were differentially expressed), while guinea pigs and C. aperea differed more strongly. Almost no overlap was found between the genes with differential expression in the different domestication events. In addition, joint analyses of all domesticated and wild samples provided only suggestive evidence for the existence of a small group of genes that changed their expression in a similar fashion in different domesticated species. The most extreme of these shared expression changes include up-regulation in domesticates of SOX6 and PROM1, two modulators of brain development. There was almost no overlap between gene expression in domesticated animals and the tame and aggressive rats. However, two of the genes with the strongest expression differences between the rats (DLL3 and DHDH) were located in a genomic region associated with tameness and aggression, suggesting a role in influencing tameness. In summary, the majority of brain gene expression changes in domesticated animals are specific to the given domestication event, suggesting that the causative variants of behavioral domestication traits may likewise be different.

Ticks (Acari: Ixodidae) parasitizing endemic and exotic wild mammals in the Esteros del Iberá wetlands, Argentina

Five species of ticks belonging to the genera Amblyomma, Haemaphysalis and Rhipicephalus were recorded from endemic and exotic wild mammals in the Esteros del Iberá wetlands, Argentina. Adults and immature stages of Amblyomma dubitatum were found on Hydrochoerus hydrochaeris, Sus scrofa, Axis axis and Myrmecophaga tridactyla. Larvae and nymphs of A. dubitatum were collected on Bubalus bubalis, Lepus europaeus, Monodelphis dimidiata and on the rodents Cavia aperea, Scapteromys aquaticus, Oligoryzomys flavescens and Akodon azarae. One male of Amblyomma nodosum was associated with M. tridactyla; specimens of Haemaphysalis juxtakochi were found on A. axis, S. scrofa and Mazama gouazoubira; and Rhipicephalus (Boophilus) microplus was detected on Blastocerus ichotomus. Adults of Amblyomma triste were collected on B. dichotomus, S. scrofa and H. hydrochaeris, while immatures of this tick were recorded on M. dimidiata, A. azarae, S. aquaticus, O. flavescens and H. hydrochaeris. In addition to elucidating tick-host associations, the findings of this survey are biomedically important. Although the tick fauna of Esteros del Iberá is limited, some species, such as A. triste and R. (B.) microplus, are recognized vectors of pathogenic agents infecting humans and animals. Also, a large number of the Esteros del Iberá collection records were for ticks from exotic (S.scrofa, A. axis, B. bubalis, L. europaeus) or reintroduced (M. tridactyla) mammals, suggesting that the introduction of these mammals may result in the amplification of tick populations in the study area, withpotential deleterious effects on the endemic fauna.

The rich acoustic repertoire of a precocious rodent, the wild cavy Cavia aperea

The Caviomorph rodents have precocious young and vary in social complexity, resorting to acoustic communication to efficiently regulate social interactions intra-group and to avoid intruders and predators. The wild cavy Cavia aperea, one of the species with the largest geographic distribution, is considered a wild representative of the domestic Cavia porcellus, a species with a remarkable acoustic repertoire. We conducted a descriptive study on the acoustic behaviour of a captive population of C. aperea. We observed animals in groups, in pairs and isolated pups, and conducted sonographic and descriptive analyses. Ten distinct call types were identified: teeth-chattering, structurally variable contact calls, whines and squeals, a scream, alarm whistle, almost exclusive pup-isolation whistle and tweet calls, and the previously described alarm drrr and courtship purr calls. As in other caviomorphs, some of these signals may carry information about specific contexts and moods and others may communicate arousal. The similarity of this repertoire size to that of C. porcellus shows that the richness of the latter is not a product of domestication. Instead, it may be associated with a relatively complex social life and other ecological factors. Our data set the groundwork for comparative studies of the evolution of acoustic communication.

Comparative allometric investigations on the skulls of wild cavies (Cavia aperea) versus domesticated guinea pigs (C. aperea f. porcellus) with comments on the domestication of this species

Bivariate allometric calculations were performed to quantitatively compare skulls of wild cavies with domesticated guinea pigs. Descendents of wild caught Cavia aperea from eastern regions of the species’ distribution area were used, as well as unselected domesticated breeds of guinea pigs differing in outer appearance. The individuals of both groups were kept under similar environmental conditions. Altogether 19 parameters on the skulls and the body weights were used for the analyses. These parameters were studied in relation to greatest skull length and to body size. As a general result the diverse parameters are in most cases significantly different between both groups which is interpreted as a special result of unconsciously selected and genetically determined intraspecific changes concomitant with domestication. The skull does not change in total under the domestication process but in a mosaic manner. However, for the mosaic changes of the diverse parameters in relation to skull length a different picture is valid as related to body weight. This is caused by the fact that the skull of guinea pigs is around 5% shorter independent of the body size, a common effect of domestication also described for other species. Thus, skull length is not an appropriate parameter for body size with respect to such intraspecific investigations, although normally used for the characterization of species in interspecific comparisons of museum materials.Altogether in relation to body weight most of the parameters describing the fascial portion of the skull are shorter in the guinea pig, especially the palatine, the diastema and the mandible but also the nasalia and frontalia lengths as well as the breadth of the rostrum and the zygomaticum are smaller. Most of the occipital skull measures are additionally smaller in the guinea pigs. This is clearly the case for the length and the breadth of the braincase and for the tympanic bulla. The braincase volume is 16.2% smaller, a value only slightly different when compared with the degree of brain size decrease due to domestication as reported for this species in other investigations.

Sex-specific impact of prenatal stress on growth and reproductive parameters of guinea pigs

Body condition and reproductive maturation are parameters of reproductive success that are influenced by sexual hormones rising in the circulation during the time of puberty. Various endocrine systems can be programmed by conditions experienced during early life. Stress for instance is supposed to be capable of influencing fetal development, leading to adjustments of offspring's later physiology. We examined whether prenatal stress (induced by exposure to strobe light) during early- to mid-gestation was capable of affecting later reproductive parameters in guinea pigs (Cavia aperea f. porcellus). Therefore, we measured the levels of testosterone and progesterone from the age of day 12-124 in prenatally stressed (PS, n=20) and unaffected control animals (n=24). Furthermore, we determined the timing of puberty and growth. Body weight development revealed significantly faster growth in PS females compared to control animals. The onset of first estrus was slightly earlier in PS females, however not significantly so. Cycle lengths and levels of progesterone differed between groups over the course of time with higher progesterone levels and more constant cycles among PS females compared to control females who displayed marked differences between first and subsequent cycles. Levels of testosterone did not differ between groups. We conclude that prenatal stress accelerates growth and maturity in females, but not in males.

Guinea pigs experimentally infected with vaccinia virus replicate and shed, but do not transmit the virus

The origin of vaccinia viruses (VACV) associated with vesicular disease in cattle and humans in Southeast Brazil remains uncertain, yet the role of wild species in virus transmission has been suggested. This study investigated the susceptibility and transmission potential by guinea pigs (Cavia porcellus) - phylogenetically close to an abundant Brazilian rodent (Cavia aperea) - to two VACV strains (P1V and P2V) isolated from an outbreak of cutaneous disease in horses in Southern Brazil. Eight guinea pigs inoculated intranasally with P1V and P2V (10(6) TCID50.ml-1) did not develop clinical signs, but six animals shed virus in nasal secretions (day 1 to 9 post-inoculation - pi), developed viremia (between days 1 and 10 pi) and seroconverted to VACV. In spite of virus replication and shedding, the virus was not transmitted to sentinel animals by direct or indirect contact (aerosols) or through food and water contaminated with virus. These results demonstrate that, in spite of replicating and shedding the virus, guinea pigs do not transmit the virus upon experimental inoculation. This finding makes unlikely a possible participation of related species in VACV maintenance and transmission in nature.

Small mammals (Didelphimorphia, Rodentia and Chiroptera) from Pampean Region, Argentina

We studied small mammal assemblages recovered from owl pellets collected at 11 locations throughout the Argentina’s Pampean Region. We identified 21 species, including two marsupials, one bat, and 18 rodents. From the analysis of this dataset, we could distinguish three main groups of small mammals that currently inhabit the Pampean Region: 1) a group of taxa related to Pampean agroecosystems (Calomys spp., Akodon azarae, and Oligoryzomys flavescens); 2) a group of Brazilian species (Cavia aperea, Oxymycterus rufus, Necromys lasiurus, Necromys obscurus, Holochilus brasiliensis, and Monodelphis dimidiata); and 3) a group including species from Patagonia, Espinal and Monte phytogeographic provinces (Microcavia australis, Oligoryzomys longicaudatus, Eligmodontia typus, Graomys griseoflavus, and Akodon molinae). In addition, we documented the first record of a species of the large-bodied group of Calomys in Buenos Aires province, expanding its distribution ca. 420 km southward.

Descrição do sincrânio de Cavia aperea (Rodentia, Caviidae) e comparação com as demais espécies do gênero no Brasil

O gênero Cavia inclui quatro espécies no Brasil, C.aperea (pelo menos duas subespécies, C.a.aperea e C.a.pamparum), C.magna, C.intermedia e C.fulgida. Visando contribuir para o conhecimento da anatomia e para a distinção dessas espécies, descreve-se o sincrânio (crânio e mandíbula) de exemplares de C.a.pamparum do Rio Grande do Sul e compara-se com exemplares de C.magna deste estado e de Santa Catarina, C.intermedia da ilha de Moleques do Sul, na costa catarinense, e C.fulgida de Minas Gerais e Paraná. Cavia aperea possui crânio baixo e longo; rostro comprimido lateralmente; constrição interorbital marcada; órbita elíptica com ampla comunicação com a fossa temporal; forâmen infra-orbital amplo e deprimido; mandíbula longa e baixa, com processo angular não refletido lateralmente; fórmula dentária 1I.0C.1P.3M; dentes hipselodontes; molariformes formados por dois prismas, o anterior laminar e o posterior cordiforme. Cavia aperea distingue-se de C.magna pelo menor desenvolvimento da porção rostral do crânio e da raiz ventral do processo zigomático do maxilar; forâmen infraorbital mais deprimido; porção posterior dos frontais e parietais menos convexos; apófises paraoccipitais mais curtas e curvas anteriormente; incisivos superiores mais estreitos e geralmente opistodontes (proodontes em C.magna); fenda terciária externa (fte) mais profunda e com mais cemento; prolongamento anterior à fte mais desenvolvido e constrição na base do prolongamento posterior. Cavia intermedia possui jugal curto; fossa jugal reduzida/ausente; depressão na região interorbital bem marcada; crista sagital larga; constrição lateral no basisfenóide tênue; forâmen magno amplo; supra-occipital baixo; fte rasa e prolongamento anterior pouco desenvolvido; p4 com prisma posterior tão largo quanto o anterior; m3 com prisma anterior mais largo que o posterior e fenda secundária interna menos profunda. Cavia fulgida caracteriza-se por suas dimensões menores e fte muito profunda. Entretanto, exemplares do sul do Brasil com estes caracteres, mas coloração não típica de C.fulgida, podem pertencer à C.aperea, sendo necessários mais estudos para esclarecer esta questão.

Effects of prenatal stress on hypothalamic–pituitary–adrenal (HPA) axis function over two generations of guinea pigs (Cavia aperea f. porcellus)

Prenatal stress can alter hypothalamic–pituitary–adrenal axis function with potential consequences for later life. The aim of our study was to examine in guinea pigs (Cavia aperea f. porcellus) the effects of stress experienced during F0 pregnancy on glucocorticoid levels in plasma and feces, as well as challenge performance, in F1 offspring (n=44) and fecal glucocorticoid levels in F2 offspring (n=67). F1 animals were either born to F0 dams that had been stressed with strobe light during early to mid pregnancy, resulting in a short term increase but long-term down-regulation of maternal glucocorticoid levels, or to undisturbed F0 dams. The same stressor was used as a challenge for F1 offspring at age 26days and around 100days. Basal plasma cortisol concentrations during early F1 development, as well as overall glucocorticoid levels at challenge tests, were lower in F1 animals that were prenatally stressed than in control animals. Fecal cortisol metabolites were initially at lower levels in prenatally stressed F1 animals, relative to control animals, but shifted to higher levels around day 68, with an additional sex difference. Effects were also seen in the F2 generation, as male but not female offspring of prenatally stressed F1 animals had significantly higher levels of cortisol metabolites in feces after weaning. We conclude that stress exposure of F0 dams resulted in lower basal glucocorticoid levels in F1 offspring during the pre-pubertal phase and during stress exposure, but higher glucocorticoid levels in post-adolescent F1 animals. Also in males of F2 generation effects of stress exposure of F0 dams were detected.

Chronic stress in pregnant guinea pigs (Cavia aperea f. porcellus) attenuates long-term stress hormone levels and body weight gain, but not reproductive output

Stress, when extreme or chronic, can have a negative impact on health and survival of mammals. This is especially true for females during reproduction when self-maintenance and investment in offspring simultaneously challenge energy turnover. Therefore, we investigated the effects of repeated stress during early- and mid-gestation on the maternal stress axis, body weight gain and reproductive output. Female guinea pigs (Cavia aperea f. porcellus, n=14) were either stressed (treatment: exposure to strobe light in an unfamiliar environment on gestational day -7, 0, 7, 14, 21, 28, 35, 42) or left completely undisturbed (control) throughout pregnancy. Females of both groups received the same respective diets, and reproductive parameters were evaluated upon parturition. Additionally, hormonal data were obtained from blood and feces. The stress exposure induced a significant increase in plasma cortisol concentrations during the afternoon. In contrast to this short-term response in plasma cortisol concentrations, we found no significant differences in the levels of cortisol metabolites in feces collected after stress exposure between groups and even significantly decreased levels of fecal cortisol metabolites on non-stress days over time in treatment females. Among treatment females, gain in body weight was attenuated over gestation and body weight was lower compared to control females during lactation, especially in cases of large litter sizes. No differences could be seen in the reproductive parameters. We conclude that repeated stress exposure with strobe light during early- and mid-gestation results in a down-regulation of the hypothalamic-pituitary-adrenal axis and lower weight gain in treatment females, but has no effect on reproductive output.

A new karyotype for Cavia magna (Rodentia: Caviidae) from an estuarine island and C. aperea from adjacent mainland

We describe a new karyotype for Cavia magna Ximenez, 1980 from an estuarine island and the karyotype of Cavia aperea Erxleben, 1777 from an adjacent mainland. The species have differences in diploid number (2n), autosomal fundamental number, quantity, and distribution of heterochromatin as dissimilar distributions of the nucleolus-organizing regions (Ag-NORs). The C. aperea karyotype has a diploid number of 64 as previously reported for C. aperea and most other Cavia species. In contrast, this new C. magna karyotype exhibits a variant diploid number of 2n = 62, considering that previous work reported a karyotype of 2n = 64 for C. magna. The discovery of a distinct diploid number within C. magna represents the first record of intra-specific chromosomal variation in a species of Caviidae. The diploid number of 2n = 62, heterochromatin quantity, Ag-NOR distributions, and inversed X chromosome from this population of C. magna are as seen in the geographically proximate (Cavia intermedia Cherem Olimpio and Ximenez; intermediate Cavy). These data provide further evidence supporting C. magna as the sister species of C. intermedia.

Seasonal dynamics and hosts of Amblyomma triste (Acari: Ixodidae) in Argentina

The seasonal dynamics and host usage of Amblyomma triste in Argentina were analyzed. Adults of A. triste were present from early winter to mid-summer, with the peak of abundance from late winter to mid-spring (August to October). Larvae and nymphs were found from December to June, with the peak of abundance in summer. There were no differences among the biological parameters (pre-moult period of larvae and nymphs, pre-oviposition period of females, and minimum incubation period of eggs) of engorged ticks exposed to different photoperiod regimens at the laboratory, but the periods for each biological parameter obtained from ticks exposed in the field were significantly longer than those from the laboratory. Field results fit better with the data of seasonal distribution of each stage. Morphogenetic diapause was not detected, but complementary studies should test the presence of behavioral diapause. Rodents of the subfamily Sigmodontinae (Akodon azarae, Oligoryzomys flavescens, Oligoryzomys nigripes, Oxymycterus rufus and Scapteromys aquaticus) are the principal hosts for immature stages of A. triste, the caviid Cavia aperea could be another potential host for these stages, and birds are exceptional hosts for larvae and nymphs. Regarding hosts of adults in Argentina, domestic and wild large-sized mammals belonging to different orders (cattle, dog, horse, Blastocerus dichotomus and Hydrochoerus hydrochaeris) serve as hosts for adults of this tick species. In conclusion, A. triste has a life cycle of 1 year with adults feeding on large endemic and introduced mammals and immature stages using sigmodontine and caviid rodents as hosts.

Are the closed landfills recovered habitats for small rodents? A case study in a riparian site, Buenos Aires, Argentina

The establishment of landfills in urban areas leads to extensive disturbances. Their development after landfill closure depends on the characteristics of the soil cover, the surrounding communities and the dispersal of plants and animals. This study was carried out in a landfill closed in 2004, surrounded by an urban area, freshwater marshes and a riparian forest. The aim of this study was to determine the role that the closed landfill may play in maintaining rodent communities typical of this zone and its relation to characteristics of the sites. Four rodent and plant samplings were carried out from December 2005 to September 2006 at five sites inside the landfill: three filled cells and two areas of the riparian margin. We recorded a total of 433 individual rodents. The rodent community of the closed landfill included species typical of rural, riparian and rural habitats: Akodon azarae (358), Oligoryzomys flavescens (32), Deltamys kempi (14), Rattus rattus (14), Cavia aperea (11) and Scapteromys aquaticus (4). Rodent species composition varied among sites, but A. azarae was usually the dominant species. We found a rich rodent community mostly composed of wild species. The relictual riparian margin may have served as a major refuge for native rodent community while the landfill was in operation, and after closure it possibly acted as a source for some species to colonize the covered cells.