External tagging does not affect the feeding behavior of a coral reef fish, Chaetodon vagabundus (Pisces: Chaetodontidae)

Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of for personal use, not for redistribution. The definitive version was published in Environmental Biology of Fishes 86 (2009): 447-450, doi:10.1007/s10641-009-9545-9.Increasingly, the ability to recognize individual fishes is important for studies of population dynamics, ecology, and behavior. Although a variety of methods exist, external tags remain one of the most widely applied because they are both effective and cost efficient. However, a key assumption is that neither the tagging procedure nor the presence of a tag negatively affects the individual. While this has been demonstrated for relatively coarse metrics such as growth and survival, few studies have examined the impact of tags and tagging on more subtle aspects of behavior. We tagged adult vagabond butterflyfish (Chaetodon vagabundus) occupying a 30-ha insular reef in Kimbe Bay, Papua New Guinea, using a commonly-utilized t-bar anchor tag. We quantified and compared feeding behavior (bite rate), which is sensitive to stress, of tagged and untagged individuals over four separate sampling periods spanning four months post-tagging. Bite rates did not differ between tagged and untagged individuals at each sampling period and, combined with additional anecdotal observations of normal pairing behavior and successful reproduction, suggest that tagging did not adversely affect individuals.The authors gratefully acknowledge funding from the Fulbright Program, National Science Foundation and the Australian Research Council

Influence of Landscape Structure and Human Modifications on Insect Biomass and Bat Foraging Activity in an Urban Landscape

Urban landscapes are often located in biologically diverse, productive regions. As such, urbanization may have dramatic consequences for this diversity, largely due to changes in the structure and function of urban communities. We examined the influence of landscape productivity (indexed by geology), housing density and vegetation clearing on the spatial distribution of nocturnal insect biomass and the foraging activity of insectivorous bats in the urban landscape of Sydney, Australia. Nocturnal insect biomass (g) and bat foraging activity were sampled from 113 sites representing backyard, open space, bushland and riparian landscape elements, across urban, suburban and vegetated landscapes within 60 km of Sydney's Central Business District. We found that insect biomass was at least an order of magnitude greater within suburban landscapes in bushland and backyard elements located on the most fertile shale influenced geologies (both p<0.001) compared to nutrient poor sandstone landscapes. Similarly, the feeding activity of bats was greatest in bushland, and riparian elements within suburbs on fertile geologies (p = 0.039). Regression tree analysis indicated that the same three variables explained the major proportion of the variation in insect biomass and bat foraging activity. These were ambient temperature (positive), housing density (negative) and the percent of fertile shale geologies (positive) in the landscape; however variation in insect biomass did not directly explain bat foraging activity. We suggest that prey may be unavailable to bats in highly urbanized areas if these areas are avoided by many species, suggesting that reduced feeding activity may reflect under-use of urban habitats by bats. Restoration activities to improve ecological function and maintain the activity of a diversity of bat species should focus on maintaining and restoring bushland and riparian habitat, particularly in areas with fertile geology as these were key bat foraging habitats

Habitat Composition and Connectivity Predicts Bat Presence and Activity at Foraging Sites in a Large UK Conurbation

Background: Urbanization is characterized by high levels of sealed land-cover, and small, geometrically complex, fragmented land-use patches. The extent and density of urbanized land-use is increasing, with implications for habitat quality, connectivity and city ecology. Little is known about densification thresholds for urban ecosystem function, and the response of mammals, nocturnal and cryptic taxa are poorly studied in this respect. Bats (Chiroptera) are sensitive to changing urban form at a species, guild and community level, so are ideal model organisms for analyses of this nature. Methodology/Principal Findings: We surveyed bats around urban ponds in the West Midlands conurbation, United Kingdom (UK). Sites were stratified between five urban land classes, representing a gradient of built land-cover at the 1 km 2 scale. Models for bat presence and activity were developed using land-cover and land-use data from multiple radii around each pond. Structural connectivity of tree networks was used as an indicator of the functional connectivity between habitats. All species were sensitive to measures of urban density. Some were also sensitive to landscape composition and structural connectivity at different spatial scales. These results represent new findings for an urban area. The activity of Pipistrellus pipistrellus (Schreber 1774) exhibited a non-linear relationship with the area of built land-cover, being much reduced beyond the threshold of,60 % built surface. The presence of tree networks appears to mitigate the negative effects of urbanization for this species

Dietary overlap among coral-feeding butterflyfishes (Chaetodontidae) at Lizard Island, northern Great Barrier Reef

This study documented the range of corals,\ud and other prey types, consumed by 20 species of but-\ud terflyfishes, which co-occur at Lizard Island, northern\ud Great Barrier Reef, Australia. Six species (Chaetodon\ud aureofasciatus, C. baronessa, C. lunulatus, C. plebius,\ud C. rainfordi and C. trifascialis) fed almost exclusively\ud on scleractinian corals, and a further eight species\ud (C. citrinellus, C. kleinii, C. lunula, C. melannotus,\ud C. rafflesi, C. speculum, C. ulietensis,and C. unima-\ud culatus) took a significant proportion of their bites\ud from corals. The other six species (C. auriga, C. ep-\ud hippium, C. lineolatus, C. semeion, C. vagabundus, and\ud Chelmon rostratus) rarely consumed coral, but fed on\ud small discrete prey items from non-coral substrates.\ud Coral-feeding butterflyfishes consumed a wide range of\ud corals. Chaetodon lunulatus, for example, consumed 51\ud coral species from 24 different genera. However, there\ud was up to 72% dietary overlap between coral-feeding\ud butterflyfishes, with 11/14 species feeding predomi-\ud nantly on Acropora hyacinthus or Pocillopora dami-\ud cornis. The most specialised corallivore, C. trifascialis,\ud took 88% of bites from A. hyacinthus. Chaetodon tri-\ud fascialis defend territories encompassing one or more\ud colonies of A. hyacinthus, and may have prevented\ud other species such as C. lunulatus from feeding even\ud more extensively on this coral. This study has shown\ud that coexistence of coral-feeding butterflyfishes occurs\ud despite an apparent lack of partitioning of prey\ud resources. While different coral-feeding butterflyfishes\ud were more or less selective in their use of different coral prey, virtually all species fed predominantly on\ud A. hyacinthus or P. damicornis

Is there a reproductive basis to solitary living versus pair-formation in coral reef fishes?

Many species of coral reef fishes form pairs. While it is assumed that pairs represent the breeding unit of these species, the reproductive status of paired versus solitary individuals, and changes in status associated with pair-formation have seldom been investigated. In order to assess whether pairing is related to reproduction we examined whether the ontogenetic timing of pair formation coincided with the onset of maturation in four species of fishes: Chaetodon lunulatus and Chaetodon melannotus (family Chaetodontidae), and Valenciennea muralis and Valenciennea strigata (family Gobiidae). 65–78% of all fishes occurred in pairs. In C. lunulatus and V. muralis, pair-formation coincided with maturation, suggesting that these species form pairs for breeding. Further, C. lunulatus and V. muralis exhibited significant positive size-assortative pairing, which is often associated with monogamous mating. In contrast, pair formation in C. melannotus and V. strigata did not coincide with maturation. In both these species many solitary individuals were reproductive, and same sex pairs were common. While reproduction may be the basis for pairing in some species, both solitary and paired individuals are capable of breeding in others. We propose\ud that non-reproductive mechanisms, such as predator vigilance, may explain pair-formation in coral reef fishes\ud with non-monogamous breeding systems