Burrow Habitat Research Articles

Emersion behaviour underlies variation in gill morphology and aquatic respiratory function in the amphibious fish Kryptolebias marmoratus

Fishes acclimated to hypoxic environments often increase gill surface area to improve O2 uptake. In some species, surface area is increased via reduction of an interlamellar cell mass (ILCM) that fills water channels between gill lamellae. Amphibious fishes, however, may not increase gill surface area in hypoxic water because these species can, instead, leave water and breathe air. To differentiate between these possibilities, we compared wild amphibious mangrove rivulus Kryptolebias marmoratus from two habitats that varied in O2 availability - a hypoxic freshwater pool versus nearly anoxic crab burrows. Fish captured from crab burrows had less gill surface area (as ILCMs were enlarged by ∼32%), increased rates of normoxic O2 consumption and increased critical O2 tension compared with fish from the freshwater pool. Thus, wild mangrove rivulus do not respond to near-anoxic water by decreasing metabolism or increasing O2 extraction. Instead, fish from the crab burrow habitat spent three times longer out of water, which probably caused the observed changes in gill morphology and respiratory phenotype. We also tested whether critical O2 tension is influenced by genetic heterozygosity, as K. marmoratus is one of only two hermaphroditic vertebrate species that can produce both self-fertilized (inbred) or out-crossed (more heterozygous) offspring. We found no evidence for inbreeding depression, suggesting that self-fertilization does not impair respiratory function. Overall, our results demonstrate that amphibious fishes that inhabit hypoxic aquatic habitats can use a fundamentally different strategy from that used by fully aquatic water-breathing fishes, relying on escape behaviour rather than metabolic depression or increased O2 extraction ability.

The role of abiotic and biotic cues in burrow habitat selection by juvenile crayfish

Environmental cues contain critical information for individuals while searching for mates and suitable habitat. Crayfish have well-developed chemosensory abilities for detecting environmental cues in water; much less is known about these abilities on land. The Devil crayfish (Cambarus diogenes) is a burrowing crayfish often found in dense floodplain colonies as adults. Juveniles however are released in surface water and must navigate overland to burrow. Previous work demonstrates juveniles use cues from conspecific adults, and to a lesser extent, soil cues, for burrow site selection. Using mesocosms, we build on this by examining burrowing cues associated with (1) congeneric adults, (2) excavated burrow material and (3) other juveniles. In contrast to conspecific adults, cues provided by congeneric adults did not override cues associated with soil type. Similarly, juveniles burrowed closer to conspecific adult burrow mounds than to congeneric and human-built mounds. Juveniles also showed significant grouping behaviour in the absence of all other cues. These results suggest juvenile crayfish integrate multiple terrestrial cues for burrow site selection.

Habitat, diet, macronutrient, and fiber balance of Himalayan marmot (Marmota himalayana) in the Central Himalaya, Nepal

The Himalayan marmot (Marmota himalayana) occurs throughout the Himalayan alpine mountain ecosystem. We examined the characteristics of Himalayan marmot habitat, diet, and macronutrient consumption in the upper Mustang region of Nepal. Marmots inhabited warmer valleys close to water sources in areas between 2,900 and 4,800 m above sea level. Soil pH, organic matter, organic carbon, and phosphorus were not different in marmot use versus available habitat; however, potash levels significantly lower in marmot burrow habitat. Seventeen species of plants, including Primula spp., Potentilla fruticosa, Kobresia pygmaea, Anaphalis contorta, Lonicera spinosa, and Carex spp., were recorded in marmot scats over 3 seasons (summer 2010, autumn 2010, and spring 2011). Analysis showed a positive correlation between the total macronutrient content (dry matter protein + carbohydrate + fat) of plants and their occurrence in the diet. Analysis of the fiber and macronutrient balance of a limited number of plants consumed by ...

Habitat Selection by Crawfish Frogs (Lithobates areolatus) in a Large Mixed Grassland/Forest Habitat

Our objective was to examine breeding dispersal, burrow-use characteristics, and burrow habitat selection by Crawfish Frogs (Lithobates areolatus) in two distinct vegetation types (open grasslands and a mosaic of forest and transitioning grasslands) in southeastern Indiana, from March to August 2009 and 2010. We captured 14 frogs at their breeding ponds and tracked them to their burrows using radio telemetry. Once we identified their burrows, we compared habitat metrics at the burrows to random locations. We used an information-theoretic model selection approach to approximate the parsimony of logistic regression models comparing the habitat features of burrows to random, available sites. Frogs dispersed a straight-line average distance of 215 m and used an average of four burrows. They generally did not change burrows after June. Our top model included covariates for the number of burrows, canopy cover, and a site covariate. Our results suggested that habitat selection by Crawfish Frogs occurred hierarchically; in mixed grassland/forest habitats, they first selected areas with low canopy cover, and then selected areas with many available burrows. To manage habitat for Crawfish Frogs, we recommend preventing woody encroachment and reducing canopy cover in grassland areas occupied by Crawfish Frogs. Additionally, areas with a large number of burrows appear to provide the most suitable Crawfish Frog habitat.

Spacing patterns of a tropical forest rodent, the spiny rat ( Proechimys semispinosus ), in Panama

Spacing patterns of individuals within an island population of the Central American spiny rat Proechimys semispinosus were studied by radio-tracking eight adults for 2 months during the rainy season and eight adults for 1 month during the dry season in central Panama. All trees ≥10 cm diameter at breast height on the island were mapped, tagged, identified to species, and inventoried monthly to determine fruit production. Diurnal telemetry was conducted to locate daytime resting burrows. Burrow habitat was quantified by measuring nine variables at each burrow site. Individuals had larger home ranges and greater home-range overlap during the rainy season, and males had marginally larger home ranges than females. No evidence was found of attraction, avoidance or exclusive use of space by adult spiny rats. Thirty-six located burrows had nine instances of co-occupancy. Burrows were located close to water and had little herbaceous cover. The presence of broadly overlapping home ranges, larger home ranges of males vs females, greater numbers of burrows of females in home ranges of males vs those of females, and larger home ranges of sexually active males suggest that P. semispinosus had a promiscuous mating system within this population.

Characteristics of Burrows Used by Juvenile and Neonate Desert Tortoises (Gopherus agassizii) during Hibernation

Behavior of young tortoises released from seminatural nurseries could be affected by the length of time spent within the nursery before release. We tested whether neonate (under two months) and juvenile (8–9 years) Desert Tortoises selected hibernation burrows with differing characteristics after release from their natal pen. Burrow habitat (canopy cover and landscape slope) did not differ between age classes. Juvenile tortoises were larger than neonates and, therefore, used larger burrows than neonates, but their burrows were a closer fit to tortoise size than were the neonate burrows. Juvenile burrow orientation differed significantly from a uniform distribution, with a mean direction of 162° (SSE); the burrows of neonates were not oriented in any particular direction. Selectivity of juveniles compared to neonates may have contributed to higher levels of movement by juveniles between release and hibernation. These age-related differences in behavior should be incorporated into nursery-based management plans.