Rural roads as barriers to the movements of small mammals

MACPHERSON, D.; MACPHERSON, J.L.; MORRIS, P. 2011. Rural roads as barriers to the movements of small mammals. Applied Ecology and Environmental Research 9(2):167-180.

Abstract. Over the last 50 years increasing fragmentation of habitats has occurred due to road building. Fragmenting a large population into smaller ones can have a negative effect on population demography. In England much small mammal habitat occurs in suburban and rural areas where the majority of roads are either single track or two lanes, and traffic density is light. This study investigated the effect of minor roads on the movements of two small mammals, the wood mouse (Apodemus sylvaticus) and bank vole (Myodes glareolus). Capture-Mark-Recapture was used to study movements beside and across rural roads of two different widths. The results suggest that even small roads less than 6metres wide, with relatively little traffic, do act as partial barriers for these small mammals, reducing their movement between habitats on either side of the road. It is evident that island populations are being created as a result of road construction, even access roads within nature reserves.

Support diameter, incline, and vertical movements of four didelphid marsupials in the Atlantic forest of Brazil

CUNHA, A.A.; VIEIRA, M.V. 2002. Support diameter, incline, and vertical movements of four didelphid marsupials in the Atlantic forest of Brazil. Journal of Zoology, London 258:419-426.

Abstract. Didelphids use vertical strata in different ways, suggesting the existence of a wider variety of niches than simply arboreal or terrestrial. This variety could be related to the differential ability to deal with support diameters and inclines, and might be important for the coexistence of species in local assemblages. From data obtained with the spool-and-line technique, the use of the vertical space and above-ground supports is described in four species of an assemblage of didelphid marsupials in south-east Brazil. The stratification in this and other assemblages in the Atlantic forest and in the Amazon is also compared. Animals were trapped in Serra dos Órgãos, state of Rio de Janeiro, and equipped with a spool-and-line device before release. The paths were tracked by measuring variables related to support diameter, incline, distance and height moved above ground. The diameter of supports used was positively related to body size, and the incline to the dominant direction of movement (horizontal vs vertical). The more cursorial species, Metachirus nudicaudatus, only once moved above ground in > 3200 m of paths followed. Didelphis aurita moved mostly on the ground, but was the only species that occasionally reached the canopy. Philander frenata also moved mostly on the ground, occasionally used the understorey, but never reached the canopy. The more arboreal species, Marmosops incanus, moved mostly in the understorey, but never in the canopy. This pattern of stratification is similar to that observed in other sites in the Atlantic forest and in the Amazon.

A radio tracking study of home range and movements of the marsupial Micoureus demerarae (Thomas) (Mammalia, Didelphidae) in the Atlantic forest of south-eastern Brazil

JUNIOR, E.A.M.; CHIARELLO, A.G. 2005. A radio tracking study of home range and movements of the marsupial Micoureus demerarae (Thomas) (Mammalia, Didelphidae) in the Atlantic forest of south-eastern Brazil. Revista Brasileira de Zoologia 22(1):85-91.

Abstract. From August 2001 to July 2002 the home range and movements of seven Micoureus demerarae (Thomas, 1905) (three males and four females) were investigated using radio tracking in the União Biological Reserve, state of Rio de Janeiro, south-eastern Brazil. A total of 436 locations was obtained and home range estimated with fixed Kernel (95% of data points), and minimum convex polygon (MCP) methods, with 100 and 95% of data points. Male home ranges estimated by MCP (100%) ranged from 5.4-24.2 ha and females from 0.3-10.7 ha. Corresponding figures calculated with Kernel (95%) were 4-10.9 ha for males and 1.3-5.9 ha for females. Animals travelled on average 423 m/night, with males travelling significantly further (582.8 m/night) than females (335.1 m/night) (t test, t = 3.609, p = 0.001). We concluded that radio tracking produced much larger home ranges than those estimated with traditional live-trapping techniques, suggesting that the latter might underestimate ranging when the area covered with traps is relatively small (ca. 1 ha or less). Radio tracking also indicated that M. demerarae, although predominantly arboreal and weighting only ca. 130 g., has movements similar in magnitude to larger-sized terrestrial didelphimorph marsupials, such as Didelphis Linnaeus, 1758, Philander Linnaeus, 1758 and Metachirus (Desmarest, 1817).

A demo-genetic analysis of a small reintroduced carnivore population: the otter (Lutra lutra) in the Netherlands

SEIGNOBOSC, M.; HEMERIK, L.; KOELEWIJN, H.P. 2011. A demo-genetic analysis of a small reintroduced carnivore population: the otter (Lutra lutra) in the Netherlands. International Journal of Ecology, v. 2011, Article ID 870853, 11 pages. doi: 10.1155/2011/870853.

Abstract. Assessing the viability of reintroduced animal populations is a complicated task. Reintroductions are usually carried out with a small number of individuals, thereby, limiting the possibilities for monitoring because of the possible negative effects of intensive monitoring on survival and reproduction. Moreover, reintroduction studies are part of a socioeconomic interplay of forces, thereby, also limiting monitoring possibilities. Also, knowledge of population demography and abundance can be incomplete or unattainable. Here, we illustrate how we combined traditional telemetry and novel non-invasive genetic methodology to construct a detailed life table of a small reintroduced otter population in The Netherlands. Combining an appropriate capture-mark-recapture framework with a matrix modelling approach provides, in general, useful insights for such populations. The data indicated that (i) male survival is lower than female survival, (ii) the reintroduced population is currently growing (estimated λ = 1.26: range [1.06, 1.42]) and seems viable, (iii) increasing adult survival is currently the critical stage at which efforts of field managers should concentrate, and (iv) the modelling framework allowed us to determine the boundary conditions for the vital rates under which the population would go extinct. The applied approach directs at measurements that help field managers to implement the right conservation strategy after reintroductions.

Rodent handling of Araucaria araucana seeds

SHEPHERD, J.D.; DITGEN, R.S. 2013. Rodent handling of Araucaria araucana seeds. Austral Ecology 38:23-32. doi: 10.1111/j.1442-9993.2012.02366.x.

Abstract. In an intermast year of very low seed production, we studied seed handling in an Araucaria araucana (Araucariaceae) forest in Neuquén Province, Argentina. Rodents identified in 844 photographs from automatic cameras removed 589 seeds marked with small embedded magnets.Within 12 days of removal, 460 were recovered using a magnetic field locator; 79% of recoveries were from burrows and caches in litter or soil. Rodents exhibited a diversity of seed-handling strategies and differed in their potential as dispersal agents. Seed removal was most likely between 15.00 hours and 21.00 hours, but diurnal and nocturnal visits were recorded for all species. Oligoryzomys longicaudatus (Cricetidae) was a seed predator that took 8% of marked seeds and left none whole. Chelemys macronyx (Cricetidae) and Rattus norvegicus (Muridae) removed 25% and 19% of marked seeds respectively.These two species deposited the majority of seeds in groups of 10 or more in burrow larders that were unfavourable seedling establishment sites far from daylight. Abrothrix longipilis (Cricetidae) removed 43% of seeds, scatter-hoarded the largest percentage of whole seeds (37%), moved some seeds farther than 40 m, and left them in favourable seedling establishment sites near daylight. For all species, the number and proportion of seeds cached whole increased as more seeds were removed. Rodents, especially A. longipilis, may play an important role in regeneration of A. araucana. Seed-handling strategies and potentially effective dispersal are discussed in terms of masting seed production.

Jumping ability in the arboreal locomotion of didelphid marsupials

DELCIELLOS, A.C.; VIEIRA, M.V. 2009. Jumping ability in the arboreal locomotion of didelphid marsupials. Mastozoología Neotropical 16(2):299-307.

Abstract. Didelphid marsupials are considered to cross discontinuities between arboreal supports using a cautious locomotion, using the prehensile tail as fifth limb. However, this ability was only described for Caluromys philander. We describe and compare the locomotory performance and postural behavior of seven species of didelphid marsupials crossing discontinuities between artificial supports representing arboreal gaps. Individuals were captured in areas of Atlantic Forest in Rio de Janeiro State, Brazil. Animals were stimulated to jump from a fixed horizontal support one meter above the ground to an inclined support of same diameter. We measured the maximum distance of jump (40, 60, 80 or 100 cm) and reach or distance actually reached by the jump. Arboreal species (Marmosops incanus, Gracilinanus microtarsus, Micoureus paraguayanus, and C. philander) jumped longer distances and had longer relative reach in jumps than semi-terrestrial species (Didelphis aurita, and Philander frenatus). Only the specialized terrestrial Metachirus nudicaudatus did not jump in the tests. The relation between absolute reach and body size was weak and non significant. This study did not corroborate the view that didelphid marsupials cross discontinuities between arboreal supports only through a cautious locomotion, without jumping. On the contrary, we identified patterns of jumping performance and behavior of didelphid marsupials related to their use of the vertical strata.

Frequency of movements of small mammals among Atlantic Coastal Forest fragments in Brazil

PIRES, A.S.; LIRA, P.K.; FERNANDEZ, F.A.S.; SCHITTINI, G.M.; OLIVEIRA, L.C. 2002. Frequency of movements of small mammals among Atlantic Coastal Forest fragments in Brazil. Biological Conservation 108:229-237.

Abstract. Rates of interfragment movements were estimated for small mammals inhabiting a group of eight Atlantic Coastal Forest fragments, surrounded by grassland matrix, in order to understand the degree to which each species' population was isolated. Didelphis aurita showed the greatest movement rate (19.4% of recaptures showing interfragment movements), followed by Metachirus nudicaudatus (10.0%), Philander frenata (7.5%), Nectomys squamipes (3.6%), Micoureus demerarae (1.2%) and Akodon cursor (0.25%). Interfragment movements were not detected for Caluromys philander, Oecomys concolor and Oligoryzomys nigripes. Species can be placed along a continuum which goes from species that are represented by a single population in the whole study area, through those with metapopulations, to species that have isolated populations in each fragment. Ability to move among fragments was not related to abundance in the matrix; nevertheless, such ability helps to explain the persistence of species in fragments otherwise too small to support viable populations.

Microtus population biology: demographic changes in fluctuating populations of M. ochrogaster and M. pennsylvanicus in southern Indiana

KREBS, C.J.; KELLER, B.L.; TAMATIN, R.H. 1969. Microtus population biology: demographic changes in fluctuating populations of M. ochrogaster and M. pennsylvanicus in southern Indiana. Ecology 50(4):587-607.

Abstract. Microtus pennsylvanicus and M. ochrogaster are sympatric in southern Indiana grasslands. From June 1965 to August 1967 four populations were live trapped, three of them in 0.8-hectare (2-acre) outdoor pens. Both species increased during 1965 and reached peak densities in summer 1966. Microtus ochrogaster declined abruptly that fall and remained low; M. pennsylanicus declined the following spring.
One of the fenced populations increased to a density about three times that of its unfenced control. By early fall 1966 it had nearly destroyed its food resources and then suffered a severe decline associated with obvious overgrazing and starvation. No such overgrazing has been seen on any unfenced grasslands in this area. Dispersal is probably necessary for normal population regulation in these voles, since fenced populations seem unable to regulate their density below the limit set by starvation.
Both species bred extensively in the winter of 1965-66 during the phase of population increase. There was little or no breeding during the winter after the peak.
Survival of females in the trappable population of both species was high and relatively constant until the end of the cycle. In males, periods of low survival punctuated the increase and peak phases, and these periods of low male survival did not occur at the same time in the two Microtus species. Some mortality processes are thus higly specific for sex and species. In the fenced populations survival rates were very high and no sporadic male losses occurred.
Increasing and peak populations of M. pennsylvanicus and M. ochrogaster are characterized by adults of large body size. During the increase and peak phases some voles stopped growing at low weights (30-40 g) while others reached high aymptotic weights (45-55 g).
The demography of these Microtus species in southern Indiana is similar to that of other cyclic voles and lemmings in temperate and arctic areas.

Habitat fragmentation and movements of three small mammals (Sigmodon, Microtus, and Peromyscus)

DIFFENDORFER, J.E.; GAINES, M.S.; HOLT, R.D. 1995. Habitat fragmentation and movements of three small mammals (Sigmodon, Microtus, and Peromyscus). Ecology 76(3):827-839.

Abstract. We studied the effects of habitat fragmentation on the movements of cotton rats (Sigmodon hispidus), deer mice (Peromyscus maniculatus), and prairie voles (Microtus ochrogaster) living in a fragmented landscape using 7.7 yr (1984-1992) of mark-recapture data. The study area included three kinds of 0.5-ha blocks: single large patches (5000 m²), clusters of medium patches (288 m²), and clusters of small patches (32 m²). We tested three predictions regarding animal movements. First, animal should move longer distances as fragmentation increases. Second, the proportion of animals moving will decrease as fragmentation increases. Third, species will show more movement from putative sources to putative sinks. In support of our first two predictions, all species (except male cotton rats) moved farther, and lower proportions of animals moved, as fragmentation increased. In testing our third prediction, we found no trends, for all species, between patch size and the net number of animals a block either imported or exported, indicating source-sink dynamics were probably not occurring on our study site. Furthermore, animals of all species (except female deer mice) switched more frequently to blocks of larger patches. For prairie voles in the spring and deer mice in the summer, relative abundance among blocks predicted from a Markov matrix model of switching probabilities showed high congruence with the actual abundances, indicating movement and abundance were related. In both cotton rats and prairie voles but not in deer mice, more juveniles and nonreproductive animals switched between blocks than did adults or reproductive animals. Deer mice switched more frequently than did either cotton rats or prairie voles; the latter species switched in similar frequencies. We discuss the implications of our data for modeling and conservation.

Movement distances of five rodents and two marsupial species in forest fragments of the coastal Atlantic Rainforest, Brazil

PÜTTKER, T.; MEYER-LUCHT, Y.; SOMMER, S. 2006. Movement distances of five rodents and two marsupial species in forest fragments of the coastal Atlantic Rainforest, Brazil. Ecotropica 12:131-139.

Abstract. Movement distances provide information on diverse population biological parameters and are essential in understanding the ecology of a species. Mean distances moved between successive captures (SD), distribution of movement distances, and the mean maximum distances moved (MMDM) were investigated in five rodent and two marsupial species in forest fragments of the coastal Atlantic rainforest (Mata Atlântica) in the state of São Paulo, Brazil. The investigated species were the rodents Akodon montensis (Thomas, 1902), Oligoryzomys nigripes (Olfers, 1818), Delomys sublineatus (Thomas, 1903), Oryzomys russatus (Wagner, 1848), and Thaptomys nigrita (Lichtenstein, 1829), and the marsupials Marmosops incanus (Lund 1840), and Gracilinanus microtarsus (Wagner, 1842). Akodon montensis differed significantly from all other species and moved the lowest SD and MMDM. The marsupials differed significantly from most of the rodents and moved the largest SDs. All species showed the highest frequency of movements in a distance class of 0–20 m. Differences between sexes in SD was detected for O. nigripes, O. russatus, and G. microtarsus, males moving significantly longer distances than females. The different study sites had no influence on SD in any of the investigated species. Only the males of G. microtarsus showed a seasonal variation in SD, moving longer distances during reproductive activity.

Water absorption of the fur and swimming behaviour of semiaquatic and terrestrial oryzomine rodents

SANTORI, R.T.; VIEIRA, M.V.; ROCHA-BARBOSA, O.; MAGNAN-NETO, J.A.; GOBBI, N. 2008. Water absorption of the fur and swimming behaviour of semiaquatic and terrestrial oryzomine rodents. Journal of Mammalogy 89(5):1152-1161.

Abstract. Locomotion in land and water requires different adaptations, hence semiaquatic mammals must deal with conflicting demands of the 2 environments. Semiaquatic rodents of the tribe Oryzomyini are considered semiaquatic mostly based on habitat use and morphology, but locomotory specializations were not yet determined for most species of the group. We compared water absorption of the fur and swimming behavior between 2 species of oryzomyine water rats (Nectomys) and 2 terrestrial species of Cerradomys. We used adult rodents captured in the wild but acclimated to laboratory conditions. Water absorption rate was determined by the relative increase in body mass after a 5-min swimming session. Animals were videotaped swimming in an aquarium to determine gaits, body posture, maneuverability, and speed. Water absorption rate was significantly lower in semiaquatic species, with no significant difference between sexes. Bipedal paddling was the more frequently used gait by all 4 species, but semiaquatic species were faster and maintained a more hydrodynamic body posture, with a short gliding phase during the gait cycle. Only semiaquatic species were capable of floating effortlessly, and used the swimming bound, a gait similar to the half bound of terrestrial locomotion. Submerged swimming was the fastest swimming gait, used by 1 terrestrial and 1 semiaquatic species. The better performance during bipedal swimming of semiaquatic water rats was related to the improved buoyancy provided by reduced water absorption of the fur, which seemed to represent an important adaptation to move in the water without compromising locomotion on land.

Arboreal walking performance in seven didelphid marsupials as an aspect of their fundamental niche

DELCIELLOS, A.C.; VIEIRA, M.V. 2006. Arboreal walking performance in seven didelphid marsupials as an aspect of their fundamental niche. Austral Ecology 31:449-457.

Abstract. Species of didelphid marsupials (Didelphimorphia, Didelphidae) differ in their use of the forest strata, but it is not clear whether these differences are in fundamental or realized niches. The fundamental niche of seven species of didelphids (Caluromys philander, Didelphis aurita, Gracilinanus microtarsus, Marmosops incanus, Metachirus nudicaudatus, Micoureus demerarae, and Philander frenatus) was compared using their performance in arboreal walking. The association between performance and vertical use of the forest also was tested accounting for phylogenetic and allometric effects. Tests consisted of making the animal cross five 3 m long horizontal supports of different diameters, 1 m from the ground. The cycle of maximum speed was chosen to measure stride length, frequency and velocity. Arboreal species performed better than the terrestrial ones, but a major part of the variation in stride length (70.95%) and stride frequency (88.10%) was associated with body size. Part of the variation in stride length independent of body size (14.05%) was associated with the degree of vertical use of the forest, after phylogenetic effects were accounted for. Fundamental niches of six of the seven species were discriminated with the performance tests used. Discrepancies between the realized and fundamental niches can be inferred for two of these species, D. aurita and P. frenatus.

Movement distances and density estimation of small mammals using the spool-and-line technique

MENDEL, S.M.; VIEIRA, M.V. 2003. Movement distances and density estimation of small mammals using the spoll-and-line technique. Acta Theriologica 48(3):289-300.

Abstract. Edge effect is an inherent problem when using trapping grids to estimate density of small mammals, resulting in a sampling area larger than the area of the grid. Distances between captures of individuals are used to estimate A(W), the effective sampling area of a trapping grid, but grid size sets a limit for the largest detectable distance. The spool-and-line technique is proposed here as a new method to estimate A(W). Movement distances based on the spool-and-line technique were compared to similar movement distances based on capture-recapture of three spacies of marsupials of the Atlantic Forest of Brazil. Distances based on the two methos were uncorrelated, and only ln-transformed distances based on the spool-and-line were normally distributed. The maximum distance moved (MaxD) estimated by the spool-and-line was chosen as the more accurate and practical distance to estimate edge effect. Estimates of the effective sampling area and densities for the common opossum Didelphis aurita (Wied-Neuwied, 1826), were compared using MaxD based on spool-and-line (MaxDspool), capture-recapture (MaxDcap), and also the distance between traps (DT). MaxDspool reflected more accurately density variation between seasons. Movement distances of small mammals based on the spool-and-line technique permit more accurate estimates of density and its dynamics.