Video Playback Versus Live Stimuli for Assessing Mate Choice in a Pipefish

Synopsis In this study, I investigated the application of the video playback technique to studies on mate choice in the pipefish, Syngnathus typhle. In this sex-role reversed species, the males are predominately the choosing sex, and given a choice, prefer to mate with larger females. As such, I tested if this known mate preference remained when using this novel experimental technique. Specifically, I compared the response of males to video images of females to that of live females. Results revealed that male pipefish showed a stronger preference for the larger female in the video playback treatment than in the clear glass (two-way interaction) live female treatment. This experiment has, therefore, demonstrated that the pipefish respond in the predicted direction in response to video playback, and as such proves to be a reliable method to study mate preferences in this species.     

A solar-powered transmitting video camera for monitoring cliff-nesting raptors

ABSTRACT.   We designed a system of solar-powered video cameras that transmitted images via telemetry to a monitor. This system allowed us to study the breeding behavior of the Bearded Vulture ( Gypaetus barbatus ) in the Pyrenees (northeastern Spain). From 2000 to 2004, 12 nests in seven territories were equipped with video cameras. To avoid disturbing the birds, equipment was installed 3–8 weeks before egg-laying. The acceptance rate was 75%. No decline in productivity was observed for nests monitored with video cameras compared to control nests. The cameras enabled us to document egg-laying, hatching asynchrony, the nestlings' diet, and the parents' breeding behavior from distances of 2–3 km, although technical problems temporarily interrupted the transmission of images. Video cameras can be used successfully to study the Bearded Vultures, and probably other cliff-nesting raptors, without reducing productivity.     

An evaluation of the efficacy of video displays for use with chimpanzees (Pan troglodytes)

Video displays for behavioral research lend themselves particularly well to studies with chimpanzees (Pan troglodytes), as their vision is comparable to humans', yet there has been no formal test of the efficacy of video displays as a form of social information for chimpanzees. To address this, we compared the learning success of chimpanzees shown video footage of a conspecific compared to chimpanzees shown a live conspecific performing the same novel task. Footage of an unfamiliar chimpanzee operating a bidirectional apparatus was presented to 24 chimpanzees (12 males, 12 females), and their responses were compared to those of a further 12 chimpanzees given the same task but with no form of information. Secondly, we also compared the responses of the chimpanzees in the video display condition to responses of eight chimpanzees from a previously published study of ours, in which chimpanzees observed live models. Chimpanzees shown a video display were more successful than those in the control condition and showed comparable success to those that saw a live model. Regarding fine-grained copying (i.e. the direction that the door was pushed), only chimpanzees that observed a live model showed significant matching to the model's methods with their first response. Yet, when all the responses made by the chimpanzees were considered, comparable levels of matching were shown by chimpanzees in both the live and video conditions.     

Quantitative Locomotion Study of Freely Swimming Micro-organisms Using Laser Diffraction

Soil and aquatic microscopic organisms live and behave in a complex three-dimensional environment. Most studies of microscopic organism behavior, in contrast, have been conducted using microscope-based approaches, which limit the movement and behavior to a narrow, nearly two-dimensional focal field.¹ We present a novel analytical approach that provides real-time analysis of freely swimming C. elegans in a cuvette without dependence on microscope-based equipment. This approach consists of tracking the temporal periodicity of diffraction patterns generated by directing laser light through the cuvette. We measure oscillation frequencies for freely swimming nematodes.Analysis of the far-field diffraction patterns reveals clues about the waveforms of the nematodes. Diffraction is the process of light bending around an object. In this case light is diffracted by the organisms. The light waves interfere and can form a diffraction pattern. A far-field, or Fraunhofer, diffraction pattern is formed if the screen-to-object distance is much larger than the diffracting object. In this case, the diffraction pattern can be calculated (modeled) using a Fourier transform.²C. elegans are free-living soil-dwelling nematodes that navigate in three dimensions. They move both on a solid matrix like soil or agar in a sinusoidal locomotory pattern called crawling and in liquid in a different pattern called swimming.³ The roles played by sensory information provided by mechanosensory, chemosensory, and thermosensory cells that govern plastic changes in locomotory patterns and switches in patterns are only beginning to be elucidated.⁴ We describe an optical approach to measuring nematode locomotion in three dimensions that does not require a microscope and will enable us to begin to explore the complexities of nematode locomotion under different conditions.     

Study of the Impact of Replacement Granularity and Associated Strategies on Video Caching

Partial caching of large media objects such as video files has been proposed recently as the caching of entire objects can easily exhaust the storage resources of a proxy server. In this paper the idea of segmenting video files into chunks and applying replacement decisions at the chunk level rather than on entire videos is examined. It is shown that a higher byte hit ratio (BHR) can be achieved by appropriately adjusting the replacement granularity. The price paid for the improved BHR performance is that the replacement algorithm takes a longer time to converge to the steady state BHR. For the segmentation of video into chunks two methods are presented. The Fixed Chunk Size segmentation scheme that is rather simple and reveals the basic trade-off between byte hit ratio (BHR) and responsiveness to changes of popularity; the Variable Chunk Size segmentation scheme that uses the request frequencies to dynamically adjust the size of the chunk and is shown to be capable of combining a small response time with high BHR. Moreover, a variation of the fixed chunk size segmentation scheme is presented, which is shown to improve its performance by switching between different chunk sizes. Video segmentation is also considered as a mechanism to provide for caching differentiation based on access costs. By employing access cost dependent chunk sizes an overall access cost reduction is demonstrated.     

Assessment of Potential Predation Costs of Male Decoration and Courtship Display in Wolf Spiders Using Video Digitization and Playback

We used video digitization and playback techniques to examine the potential predation risk of leg decorations and visual displays of male wolf spiders, which vary across the genus Schizocosa (Araneae: Lycosidae). Video images of courting males of four Schizocosa species were modified by adding or removing tufts and presented on LCD minitelevisions to the wolf spider Hogna helluo, a common predator of Schizocosa. Predatory responses of H. helluo varied significantly among stimuli and were highest for S. ocreata (which has decorative tufts and leg-waving displays) and lower for S. rovneri, S. duplex, and S. uetzi (which lack decorations and visual displays). Removal of tufts from S. ocreata significantly reduced predatory responses of H. helluo, but addition of tufts to other species had no effect. Results suggest that leg decorations may increase detection of active leg-waving displays and thereby increase predation risk.     

A biological assessment of Apophua simplicipes (Hymenoptera: Ichneumonidae) as a parasitoid of the oblique banded leafroller, Choristoneura rosaceana (Lepidoptera: Tortricidae)

Apophua simplicipes (Cresson) (Hymenoptera: Ichneumonidae) is a common parasitoid of the oblique banded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae) in organically managed apple orchards in the southern interior of British Columbia, Canada. The biological characteristics of a laboratory colony of A. simplicipes were studied. When held at 15 and 25°C and provided with honey water, individual females survived an average of 60.6±6.1 and 29.8±4.7 days, oviposited 196.7±50.7 and 326.6±51.3 eggs and parasitized a total of 163.4±40.4 and 229.4±35.8 hosts, respectively. Females oviposited into first through fourth instar oblique banded leafrollers, with significantly more parasitism occurring in the first two instars compared to the third and fourth instars. No parasitoid larvae survived past the first larval stage in parasitized fourth instar hosts. Apophua simplicipes did not parasitize larvae of three-lined leafroller, Pandemis limitata (Robinson) (Lepidoptera: Tortricidae) which is sympatric with oblique banded leafrollers in orchards in the southern interior of British Columbia. Female predation and host feeding from wounds on early instars of both leafroller species was observed under laboratory conditions. In addition, early instar hosts exited diet feeding sites in response to the probing activity of the ovipositing wasps. A similar escape reaction in the orchard may cause a leafroller larva to move away from its feeding site, making it more vulnerable to predation or movement off the tree. Apophua simplicipes larvae emerged from fifth and sixth instar hosts. Parasitized oblique banded leafroller hosts consumed significantly less meridic diet than unparasitized female larvae from fifth instar through to parasitoid emergence or leafroller pupation. Our laboratory results suggest that A. simplicipes may reduce field populations of oblique banded leafroller and decrease pest feeding damage.     

Characterization of small shallow ponds with color video imagery in Central Mexico

We present a method to evaluate ecological characteristics of small shallow ponds in Central Mexico based on video remote sensing and image processing techniques in a GIS environment. We used a set of color video imagery obtained from heights lower than 700 m above ground. Our analysis established statistical correlations between the average reflectance values contained in video imagery (digital numbers DN per Blue-Green-Red band) and the average values of limnetic variables: (1) water suspended solids concentration; (2) water turbidity; (3) total macrophytes coverage; (4) free floaters and emergent macrophytes coverage; (5) zooplankton abundance; and (6) chlorophyll-a concentration in water. We found strong correlation between DN values and vegetation presence, suspended solids concentration and water turbidity (R= 0.85 to 0.98), but weak correlations with phytoplankton and zooplankton abundance. This cheap and fast method can be used to describe general conditions of ponds related with vegetation abundance, turbidity and suspended solids.