scholarly journals Effects of Habitat Change on the Web Characteristics and Fitness of the Giant Wood Spider (Nephila pilipes) in Sri Lanka

2019 ◽  
Vol 2019 ◽  
pp. 1-6
Author(s):  
Tharaka Wijerathna ◽  
Dilini Tharanga ◽  
Inoka C. Perera ◽  
Mayuri R. Wijesinghe
Keyword(s):  
Sri Lanka ◽  
Adult Female ◽  
Prey Capture ◽  
Home Gardens ◽  
Capture Efficiency ◽  
Population Declines ◽  
Silk Thread ◽  
Close Proximity ◽  
Female Abdomen ◽  
The Web

We compare web properties and fitness of the Giant wood spider Nephila pilpes within and outside its natural rainforest habitat in Sri Lanka. The nonforest habitats comprised rural home gardens and plantations. We hypothesize that marked differences would be evident between the two habitats in (i) web properties and (ii) fitness of the female spiders. Web architectural and silk thread properties were measured in 25 webs of adult female spiders in each of the two habitats, while female abdomen size was used as the proxy for fitness. Findings support both hypotheses. The nonforest webs were more closely knit (smaller mesh spaces) and the hub was placed at higher position on the web than that in the forest webs both altering prey capture efficiency. Also, females in nonforest habitats were significantly smaller than those in the forest, indicating lowered fitness. The disparities in web characteristics and fitness are impressive given that the forest and nonforest habitats are located in close proximity, suggesting that rainforest orbweaver spiders such as Nephila pilpes may suffer population declines if the extents of natural forest continue to shrink.

scholarly journals Assessment of crop and property damage caused by Semnopithecus vetulus nestor (Bennett, 1833) (Mammalia: Primates: Cercopithecidae) in Gampaha District, Sri Lanka

2021 ◽  
Vol 13 (5) ◽  
pp. 18141-18147
Author(s):  
Sunil Wijethilaka ◽  
Lakshani S. Weerasekara ◽  
Saumya Bandara ◽  
Kithsiri B. Ranawana
Keyword(s):  
Sri Lanka ◽  
Ornamental Plants ◽  
Sri Lankan ◽  
Property Damage ◽  
Severe Problem ◽  
Governmental Organizations ◽  
Non Governmental Organizations ◽  
Close Proximity ◽  
Two Factors ◽  
Semnopithecus Vetulus Nestor

In earlier times, human-monkey interactions were not a severe problem in Sri Lanka, but has recently intensified as a result of habitat fragmentation and urbanization.  Due to these changes, Semnopithecus vetulus nestor has been listed among the 25 most Endangered primates.  The objective of our study was to evaluate the intensity of human-S.v. nestor negative interaction by identifying the crop and property damages in villages bordering Danawkanda Forest (7.001N & 80.049E), Gampaha, Sri Lanka.  We collected data using structured questionnaires interviewing households (N= 80) bordering the Danawkanda Forest from August 2014 to January 2015.  Households were most affected by damage to fruits, leaves, and buds of commercially important trees (93%), followed by damage to roof tiles (76%), and frightful confrontations with the monkeys (43%).  Average monthly loss per household from crop and property damage was estimated at between (Sri Lankan Rupees) LKR 2,700 and LKR 1,500.  Lighting firecrackers was the most common method used by the residents (99%) to deter monkeys, where as electrified barriers were rarely used (4%).  Households in close proximity to Danawkanda Forest experienced a considerable loss to their monthly income due to crop and property damage, compared to households further away.  As an alternative, residents now grow ornamental plants and short trees, eliminating the structures that attract and facilitate damage by S.v. nestor.  Awareness and active participation of residents, authorized government, and non-governmental organizations are needed to manage unplanned construction and agriculture plot extensions into the forest.  These two factors trigger the human-wildlife negative interactions in general and are not limited just to monkeys.

scholarly journals Correction to: Testing traditional hypotheses about prey capture efficiency in orb-web spiders

2020 ◽  
Author(s):  
Fernanda Carolina da Silva ◽  
Mateus Moleta ◽  
Camila Alves Dos Anjos ◽  
Gabriel Marra Schade ◽  
Gabriel Staichak ◽  
...  
Keyword(s):  
Prey Capture ◽  
Capture Efficiency ◽  
Orb Web ◽  
Orb Web Spiders

scholarly journals Chaoborus prey capture efficiency in the light and dark1

1981 ◽  
Vol 26 (3) ◽  
pp. 461-466 ◽  
Author(s):  
Michael C. Swift ◽  
Richard B. Forwarder.
Keyword(s):  
Prey Capture ◽  
Capture Efficiency

Determination of prey capture rates in the stony coral Galaxea fascicularis: a critical reconsideration of the clearance rate concept

2011 ◽  
Vol 92 (4) ◽  
pp. 713-719 ◽  
Author(s):  
Ronald Osinga ◽  
Sanne Van Delft ◽  
Muhammad Wahyudin Lewaru ◽  
Max Janse ◽  
Johan A.J. Verreth
Keyword(s):  
Clearance Rate ◽  
Prey Item ◽  
Prey Capture ◽  
Capture Efficiency ◽  
Accurate Estimation ◽  
Surrounding Water ◽  
Galaxea Fascicularis ◽  
Feeding Experiments ◽  
Total Capture ◽  
Capture Rates

In order to determine optimal feeding regimes for captive corals, prey capture by the scleractinian coral Galaxea fascicularis was determined by measuring clearance of prey items from the surrounding water. Colonies of G. fascicularis (sized between 200 and 400 polyps) were incubated in 1300 ml incubation chambers. Nauplii of the brine shrimp Artemia sp. were used as the prey item. A series of incubation experiments was conducted to determine the maximal capture per feeding event and per day. To determine maximal capture per feeding event, total uptake of nauplii after one hour was determined for different prey item availabilities ranging from 50 to 4000 nauplii per polyp. To determine maximal capture per day, the corals were subjected to four repetitive feeding events at three different prey item densities (50, 100 and 150 nauplii per polyp). Alongside these quantitative experiments, it was tested to what extent the feeding response of corals is triggered by chemical cues. One hour after food addition, extract of Artemia nauplii was added to the incubation chambers to test its effect on subsequent prey capture rates. In all experiments, prey capture was expressed as the number of nauplii consumed per coral polyp. Total capture of Artemia nauplii by G. fascicularis after a single feeding event increased linearly up till a prey item availability of 2000 nauplii per polyp. Maximal capture per feeding event was estimated at 1200 nauplii per polyp, which is higher than rates reported in previous studies. It became apparent that at high densities of Artemia nauplii, the clearance rate method does not discriminate between active capture and passive sedimentation. Repetitive feeding with 50 nauplii per polyp resulted in a constant total prey capture per feeding event. At a supply of 100 nauplii per polyp, total capture decreased after the first feeding event, and remained constant during the subsequent feeding events at a level comparable to the lower food availability. However, at a supply of 150 nauplii per polyp, total capture per event was higher throughout the entire four-hour incubation period, which obfuscates an accurate estimation of the maximal daily food uptake. In all incubations, a decrease in capture efficiency was observed within the course of the feeding event. In all repetitive feeding experiments, capture efficiency increased immediately upon addition of a new batch of food. This increase in efficiency was not caused by a priming effect of extract of Artemia. The inconsistencies in the data show that estimates of prey capture based on clearance rates should be interpreted with caution, because this method does not take into account potential dynamics of prey capture and release.

scholarly journals Population Ecology of Caribou in British Columbia

Rangifer ◽  
1996 ◽  
Vol 16 (4) ◽  
pp. 73 ◽  
Author(s):  
D.R. Seip ◽  
D.B. Cichowski
Keyword(s):  
British Columbia ◽  
Canis Lupus ◽  
Rangifer Tarandus ◽  
Population Decline ◽  
Predation Rate ◽  
Mortality Rates ◽  
Geographic Range ◽  
Population Declines ◽  
Wolf Predation ◽  
Close Proximity

The abundance and geographic range of woodland caribou (Rangifer tarandus caribou) decreased in many areas of British Columbia during the 1900's. Recent studies have found that predation during the summer is the major cause of mortality and current population declines. Increased moose {Alecs alces) populations may be related to past and current caribou declines by sustaining greater numbers of wolves (Canis lupus). Mortality rates were greater in areas where caribou calved in forested habitats, in close proximity to predators and moose. Caribou populations which had calving sites in alpine areas, islands, and rugged mountains experienced lower mortality and were generally stable or increasing. A predator-induced population decline in one area appeared to stabilize at low caribou densities, suggesting that the wolf predation rate may be density dependent.

Foraging behaviour in orb-web spiders (Araneidae): do web decorations increase prey capture success in Argiope keyserlingi Karsch, 1878?

2000 ◽  
Vol 48 (2) ◽  
pp. 217 ◽  
Author(s):  
M. E. Herberstein
Keyword(s):  
Foraging Behaviour ◽  
Prey Capture ◽  
Paired Comparison ◽  
Mortality Rates ◽  
Argiope Keyserlingi ◽  
Orb Web ◽  
Orb Web Spiders ◽  
The Web ◽  
Web Size ◽  
Prey Attraction

Orb web spiders in the genus Argiope attach highly visible silk bands called decorations or stabilimenta to their webs. Two different hypotheses regarding the function of these structures were investigated in the field using Argiope keyserlingi: prey attraction and anti-predatory device. The first hypothesis suggests that web decorations attract prey to the web, and webs carrying decorations will capture more prey than those without. A field census of prey capture showed that webs adorned with more decorative bands indeed captured more but similarly sized prey per hour compared with webs carrying fewer decorations. Web height or web size, however, were not related to the rate of prey capture. This pattern was confirmed by a paired comparison of prey-capture rates within individuals that increased or decreased the number of decorative bands on consecutive days. Individuals that used more decorations also captured more prey compared with days when they spun fewer decorations. The second hypothesis suggests that these structures function as anti-predatory devices and, consequently, spiders on decorated webs benefit from a lower rate of mortality than spiders on undecorated webs. A census of the mortality rates of spiders over 19 days revealed that spiders did not disappear from undecorated webs more frequently than from decorated webs. Consequently, the idea that web decorations act as anti-predatory devices in A. keyserlingi was not supported.

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