Morphometric and demographic differences between tropical and temperate Norway rats (<i>Rattus norvegicus</i>)

Porter, Fleur H.; Costa, Federico; Rodrigues, Gorete; Farias, Helena; Cunha, Marcelo; Glass, Gregory E.; Reis, Mitermayer Galvão dos; Ko, Albert I.; Childs, James E.

doi:10.1093/jmammal/gyv033

Cited by 19 publications

(18 citation statements)

References 32 publications

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“…We used data from previous rat studies to inform our sampling scheme and identify areas where rats were previously captured to calibrate the model (Costa et al 2014a; Porter et al 2015). Initially, 40 sites (locations at least 15m apart) within the study area were selected as potential trapping sites by spatial randomization incorporating spatial heterogeneity throughout Pau da Lima, and of these, 10 sites were chosen with the highest rat-capture success from previous sampling.…”

Section: Methods and Preliminary Resultsmentioning

confidence: 99%

A comparative assessment of track plates to quantify fine scale variations in the relative abundance of Norway rats in urban slums

et al. 2016

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Norway rats (Rattus norvegicus) living in urban environments are a critical public health and economic problem, particularly in urban slums where residents are at a higher risk for rat borne diseases, yet convenient methods to quantitatively assess population sizes are lacking. We evaluated track plates as a method to determine rat distribution and relative abundance in a complex urban slum environment by correlating the presence and intensity of rat-specific marks on track plates with findings from rat infestation surveys and trapping of rats to population exhaustion. To integrate the zero-inflated track plate data we developed a two-component mixture model with one binary and one censored continuous component. Track plate mark-intensity was highly correlated with signs of rodent infestation (all coefficients between 0.61 and 0.79 and all p-values < 0.05). Moreover, the mean level of pre-trapping rat-mark intensity on plates was significantly associated with the number of rats captured subsequently (Odds ratio1.38; 95% CI 1.19-1.61) and declined significantly following trapping (Odds ratio 0.86; 95% CI 0.78-0.95). Track plates provided robust proxy measurements of rat abundance and distribution and detected rat presence even when populations appeared ‘trapped out’. Tracking plates are relatively easy and inexpensive methods that can be used to intensively sample settings such as urban slums, where traditional trapping or mark-recapture studies are impossible to implement, and therefore the results can inform and assess the impact of targeted urban rodent control campaigns.

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Section: Methods and Preliminary Resultsmentioning

confidence: 99%

A comparative assessment of track plates to quantify fine scale variations in the relative abundance of Norway rats in urban slums

et al. 2016

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“…Indeed, the transition from growth to reproduction produces an observable relationship between age and size at maturity (Berner and Blanckenhorn, 2007). In freeliving Norway rats (R. norvegicus) from temperate and tropical populations, both males and females reach sexual maturity at ~200 g (Porter et al, 2015), suggesting this as the critical weight threshold which triggers the physiological processes that underlie the reproductive life of the species (Berner and Blanckenhorn, 2007;Porter et al, 2015). Based on this, the rats fed ad libitum (FR-) reached that threshold between the 7th and 8th week of life, while those with limited resources (FR+) matured almost a month later.…”

Section: Discussionmentioning

confidence: 99%

Growth patterns in male rats exposed to concurrent long-term environmental challenges

Cuervo¹,

Racca²,

Beldoménico³

2016

FAVE Cs Vet

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SUMMARY.Growth is a key determinant of fitness in animals, and may be affected by the environmental challenges presented over the course of an individual's lifespan. When faced with limited resources and environmental challenges, organisms may prioritize the development and maintenance of particular processes over others. To expand our understanding of the consequences of organism exposure to a changing environment, we offer a long-term experiment to compare the growth patterns of young male rats exposed and not exposed to food limitation and social conflict. The patterns of growth of young rats were altered by the exposure to these environmental challenges, two of the most frequently faced by animals. As expected, scarcity of food resulted in a marked growth decline in animals exposed to nutritional stress. Interestingly, individuals exposed to an unstable social environment, but fed ad libitum, evidenced a growth rate 6% smaller than those under stable social conditions. An interaction between food limitation and social conflict was not observed. As a larger body size growth results in a competitive advantage in encounters, the detected divergence on growth patterns may represent significant consequences on the individual's life trajectory. RESUMEN. Patrones de crecimiento en ratas macho expuestas de manera prolongada a desafíos ambientales concurrentes. En animales, la eficacia biológica es influenciada por el crecimiento, que a su vez es afectado por los desafíos ambientales que el individuo enfrente a lo largo de su vida. Ante escasez de recursos u otros desafíos, los organismos priorizarían el desarrollo y mantenimiento de algunos procesos por sobre otros. Para profundizar nuestro conocimiento sobre las consecuencias de la exposición a un ambiente cambiante, desarrollamos un experimento de larga duración para comparar los patrones de crecimiento de ratas jóvenes expuestas y no expuestas a restricción alimentaria y conflicto social. La exposición a estos dos desafíos ambientales, comunes en la naturaleza, alteró los patrones de crecimiento de las ratas. La escasez de alimento ocasionó un descenso marcado del crecimiento en los animales bajo restricción alimentaria. Mientras que individuos expuestos a inestabilidad social, pero con alimento ad libitum, demostraron una tasa de crecimiento 6% menor que aquellos en condiciones sociales estables. Adicionalmente, no se encontró interacción significativa entre restricción alimentaria y conflicto social. Siendo que un mayor crecimiento corporal resulta ventajoso ante interacciones competitivas, la diferencia detectada entre los patrones de crecimiento tendría consecuencias de importancia en la trayectoria de vida de los individuos.

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“…Heavy black rats (> 140 g) were rarely trapped in Mérida (1%), whereas in San Francisco they were abundant (35%) (Storer and Davis, 1956). Some studies have shown that island house mice and urban Norway rats from tropical regions are smaller in size compared to those from temperate regions (Berry and Scriven, 2005;Porter et al, 2015). It has been suggested that this difference could be a result of an adaptive adjustment, particularly in the absence of predators (Berry and Scriven, 2005).…”

Section: Discussionmentioning

confidence: 99%

“…However, studies on rodent populations are scarce in México and especially in tropical regions of Latin America compared to the vast information available from temperate populations. Moreover, like other rodent species that inhabit both tropical and temperate regions, population characteristics such as juvenile percentage, pregnancy rate, and weight can contrast from data described in temperate habitats (Porter et al, 2015). Ecological studies are critical to determine the dynamics of pathogen transmission within rodent populations, the risk of transmission to humans, and areas at high risk of transmission.…”

Section: Introductionmentioning

confidence: 99%

Population Characteristics of Human-Commensal Rodents Present in Households from Mérida, Yucatán, México

Panti–May¹

2016

MANTER: Journal of Parasite Biodiversity

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Anthropocommensal rodents live in close proximity to humans in many habitats around the world. They are a threat to public health because of the pathogens they carry. Recent studies in Mérida, Yucatán, México, have shown that commensal rodents harbor potential zoonotic pathogens such as bacteria, helminths, and viruses. In this study, we describe reproductive and demographic parameters of house mice and black rats present in households from Mérida, Yucatán, México, a municipality located in a tropical region in southern México. Rodents were trapped in 142 households within the municipality of Mérida from 2011 to 2014. A total of 832 rodents were trapped, constituting 556 (66.8%) house mice (Mus musculus) and 276 (33.2%) black rats (Rattus rattus). The sex ratio in mice was different than parity, while in rats it was 1:1. Mice in the weight class 8.1-12 g were most abundant in both females (52.9%) and males (57.2%). On the other hand, rats weighing ≤ 40 g (25% of females and 28.6% of males) were most abundant. The percentage of pregnancy in mice was 46.7%, whereas in rats it was 21.3%. The mean number of embryos was 4.7 and 5.8 in mice and rats, respectively. This study provides relevant demographic information on the ecology of commensal rodents from a tropical region of Latin America. We consider that our findings could be useful as a first step toward understanding the ecological behavior of rodent populations in tropical regions.

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Morphometric and demographic differences between tropical and temperate Norway rats (Rattus norvegicus)

Cited by 19 publications

References 32 publications

A comparative assessment of track plates to quantify fine scale variations in the relative abundance of Norway rats in urban slums

A comparative assessment of track plates to quantify fine scale variations in the relative abundance of Norway rats in urban slums

Growth patterns in male rats exposed to concurrent long-term environmental challenges

Population Characteristics of Human-Commensal Rodents Present in Households from Mérida, Yucatán, México

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