Vertebrate Ecology

Sundarbans (Bangladesh) mangrove forest is the largest contiguous mangrove ecosystem in the world. At 10,000 square km, it is also the largest wetland ecosystem with international importance for waterfowl habitats. The Bengal tiger (Panthera tigris tigris) is a focal species for biodiversity conservation management in the Sundarbans. Conservationists claim that Sundarbans harbors the largest population of tigers in south Asia. Sundarbans also acquired national and international protected area classifications; 23% of its total area has been designated as Sundarbans Wildlife Sanctuaries and United Nations World Heritage Sites. Use of the tiger as a keystone species and its impact on socioecological and economic considerations needs to be reviewed critically with the aim of formulating a management action plan for tiger conservation in the region.

This article provide background information pertaining to the disappearance of two sub-species of tigers from South East Asia. These wild tigers were in great numbers and used to serve as keystone species in Indonesian and Malaysian rainforest. The species are now extinct from the wild. The article reflects the fundamental anthropocentric causes that drove these tiger sub species into extinction.

The impact of alien predators on native prey populations is often attributed to prey naiveté towards a novel threat. Yet evolutionary theory predicts that alien predators cannot remain eternally novel; prey species must either become extinct or learn and adapt to the new threat. As local enemies lose their naiveté and coexistence becomes possible, an introduced species must eventually become ‘native’. But when exactly does an alien become a native species? The dingo (Canis lupus dingo) was introduced to Australia about 4000 years ago, yet its native status remains disputed. To determine whether a vulnerable native mammal (Perameles nasuta) recognizes the close relative of the dingo, the domestic dog (Canis lupus familiaris), we surveyed local residents to determine levels of bandicoot visitation to yards with and without resident dogs. Bandicoots in this area regularly emerge from bushland to forage in residential yards at night, leaving behind tell-tale deep, conical diggings in lawns and garden beds. These diggings were less likely to appear at all, and appeared less frequently and in smaller quantities in yards with dogs than in yards with either resident cats (Felis catus) or no pets. Most dogs were kept indoors at night, meaning that bandicoots were not simply chased out of the yards or killed before they could leave diggings, but rather they recognized the threat posed by dogs and avoided those yards. Native Australian mammals have had thousands of years experience with wild dingoes, which are very closely related to domestic dogs. Our study suggests that these bandicoots may no longer be naïve towards dogs. We argue that the logical criterion for determining native status of a long-term alien species must be once its native enemies are no longer naïve.

Mangrove forests are comprised of unique plant species that form the critical interface between terrestrial, estuarine, and near-shore marine ecosystems in tropical and subtropical regions. The term mangrove is generally used to describe the assemblage of trees and shrubs that grow in saline coastal habitats, normally found in the tropics and sub-tropics. Mangrove plants are not land builders but once established, play a key role in stabilization of newly accreted sediment. Mangrove tree species have developed a wide range of features, including specialized stomatal, leaf, seed, and root structures, as adaptations for living in a saline environment with high incidence of inundation. Most mangrove species are viviparous; seeds germinate while still attached to the tree. Buoyant seeds develop into mature propagules, which then drop and disperse by water. Of note is the diversity in root structures of the mangrove tree species, designed to facilitate anchorage, nutrient uptake, and gaseous exchange. Some species, such as Heritiera fomes, Sonneratia apetala, and Avicennia officinalis, have pneumataphores; upward projecting root branches that enable the gaseous exchange required for respiratory metabolism. Other species, such as Rhizophora mucronata, have “stilt” or “knee” roots for gaseous exchange, while additional features such as the “tap” roots (buttresses) of Heritiera fomes and the horizontal spread of roots in general, add to overall stability. Some plants also excrete excess salt through leaves.

Morphological approaches have been used extensively to understand assembly rules (species in-
teractions, environmental filtering, and neutral processes) that structure ecological communities. Desert
anurans cope with limited water by either being restricted to permanent water or becoming more
fossorial, which should be reflected in their morphology. We examined morphological diversity of 16 frog
species across six habitat types within the Chihuahuan Desert to investigate the relationship between
species richness and morphological space. We measured 13 morphological traits associated with loco-
motion, habitat use, and feeding. Principal components analysis separated species into three ecomor-
phological groups: fossorial, terrestrial, and semi-aquatic species. Morphological diversity was analyzed
and compared against a null model and revealed nonrandom community structure. The total assemblage
morphospace increased in relation to species richness, though this relationship was not significant.
Species were significantly packed within the morphospace exhibiting high morphological similarity
while being less evenly dispersed, with increasing species richness, indicative of a response to an
environmental gradient. Given the highly xeric nature of the Chihuahuan Desert, our results support the
assumption that environmental filtering, rather than interspecific interactions, shapes assemblages'
structure by favoring species with similar traits to co-occur more often within a given habitat type than
expected by chance.

Bengal tigers of Bangladesh are at brink of extinction due to anthropocentric disturbances. The article provide ecological perspective to help conserve the dwindling population of tigers in Bangladesh Sundarbans: the largest deltaic mangrove ecosystem in tropical belt.

Aggressive behavioural interactions between animals are widespread in nature, with ecological and evolutionary consequences of such interactions reported for both individuals giving and receiving aggression. Yet despite the importance of aggressive interactions in determining social dominance and conferring fitness benefits to successful individuals, we lack a general understanding of the conditions that influence the variation in agonistic behaviours among individuals and species. We conducted a global meta-analysis of published time-activity budgets, using a data set comprising 555 values from 88 studies, to determine variation in the time that waterbirds engaged in aggressive interactions. The mean ± SD percentage of time devoted to aggression was 2.0 ± 3.6%, with a range of 0.0-35.0%. We used our data set to test four predictions regarding avian aggression, based on the findings of earlier site-based studies. We predicted that the time spent on aggression would be influenced by four factors: (1) age class, (2) sex, (3) seasonal timing and (4) functional feeding group. A comparison of linear mixed-effects models using an information theoretic approach indicated that the proportion of time waterbirds spent engaged in aggressive interactions was best explained by the age class and sex of the focal waterbird species. More time was spent on aggression by males than females, and by adults than juveniles. We found no evidence that the time spent on aggressive behaviours varied across latitudes or body mass, with seasonal timing, sexual dimorphism, migration or breeding strategies, or between different functional feeding groups. Our findings highlight the high levels of variation in the time devoted to aggression across species, feeding groups, latitudes and seasons. Furthermore, our study demonstrates the utility of the numerous published time-activity budget studies that are available as a valuable source of data that can be used to answer broad-scale questions regarding animal behaviour.

The end-Permian mass extinction, 251 million years (Myr) ago, was the most devastating ecological event of all time, and it was exacerbated by two earlier events at the beginning and end of the Guadalupian, 270 and 260 Myr ago. Ecosystems were destroyed worldwide, communities were restructured and organisms were left struggling to recover. Disaster taxa, such as Lystrosaurus, insinuated themselves into almost every corner of the sparsely populated landscape in the earliest Triassic, and a quick taxonomic recovery apparently occurred on a global scale. However, close study of ecosystem evolution shows that true ecological recovery was slower. After the end-Guadalupian event, faunas began rebuilding complex trophic structures and refilling guilds, but were hit again by the end-Permian event. Taxonomic diversity at the alpha (community) level did not recover to pre-extinction levels; it reached only a low plateau after each pulse and continued low into the Late Triassic. Our data showed that though there was an initial rise in cosmopolitanism after the extinction pulses, large drops subsequently occurred and, counter-intuitively, a surprisingly low level of cosmopolitanism was sustained through the Early and Middle Triassic.

The West Indian manatee (Trichechus manatus) is distributed from the Atlantic coast of the United States to the center of Brazil along the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico. The species’ current distribution is more fragmented than in the past, and manatee populations are generally less abundant than they were during the last century. In Mexico, there is no specific information about the size of the manatee populations. Hence, the objective of this study was to estimate the density and abundance of manatees in the Alvarado Lagoon System (ALS) in Veracruz using distance sampling. In total, 959 systematic line transects were surveyed using a small boat. These surveys covered 90% of the ALS. Manatee density and abundance for the entire ALS was estimated at 0.23 animals/km2 (CV 34.48%) and 121 manatees (CV 34.48%), respectively. These are the first density and abundance estimates for this lagoon system and for the State of Veracruz. The extremely low number of manatees supports the urgent implementation of effective conserva¬tion measures for the species to prevent extinction of this species in Veracruz.

Waterbirds can move into and exploit new areas of suitable habitat outside of their native range. One such example is the little egret (Egretta garzetta), a piscivorous bird which has colonised southern Britain within the last 30 years. Yet, habitat use by little egrets within Britain, and how such patterns of habitat exploitation compare with native piscivores, remains unknown. We examine overlap in habitat preferences within a river catchment between the little egret and two native species, the grey heron (Ardea cinerea) and great cormorant (Phalacrocorax carbo). All species showed strong preferences for river habitat in all seasons, with other habitat types used as auxiliary feeding areas. Seasonal use of multiple habitat types is consistent with egret habitat use within its native range. We found strong egret preference for aquatic habitats, in particular freshwaters, compared with pasture and arable agricultural habitat. Egrets showed greater shared habitat preferences with herons, the native species to which egrets are most morphologically and functionally similar. This is the first study to quantify little egret habitat preferences outside of its native range.