Sound exposure changes European seabass behaviour in a large outdoor floating pen: Effects of temporal structure and a ramp-up procedure.

Underwater sound from human activities may affect fish behaviour negatively and threaten the stability of fish stocks. However, some fundamental understanding is still lacking for adequate impact assessments and potential mitigation strategies. For example, little is known about the potential contribution of the temporal features of sound, the efficacy of ramp-up procedures, and the generalisability of results from indoor studies to the outdoors. Using a semi-natural set-up, we exposed European seabass in an outdoor pen to four treatments: 1) continuous sound, 2) intermittent sound with a regular repetition interval, 3) irregular repetition intervals and 4) a regular repetition interval with amplitude 'ramp-up'. Upon sound exposure, the fish increased swimming speed and depth, and swam away from the sound source. The behavioural readouts were generally consistent with earlier indoor experiments, but the changes and recovery were more variable and were not significantly influenced by sound intermittency and interval regularity. In addition, the 'ramp-up' procedure elicited immediate diving response, similar to the onset of treatment without a 'ramp-up', but the fish did not swim away from the sound source as expected. Our findings suggest that while sound impact studies outdoors increase ecological and behavioural validity, the inherently higher variability also reduces resolution that may be counteracted by increasing sample size or looking into different individual coping styles. Our results also question the efficacy of 'ramp-up' in deterring marine animals, which warrants more investigation.

Impulsive sounds change European seabass swimming patterns: Influence of pulse repetition interval.

Seismic shootings and offshore pile-driving are regularly performed, emitting significant amounts of noise that may negatively affect fish behaviour. The pulse repetition interval (PRI) of these impulsive sounds may vary considerably and influence the behavioural impact and recovery. Here, we tested the effect of four PRIs (0.5-4.0s) on European seabass swimming patterns in an outdoor basin. At the onset of the sound exposures, the fish swam faster and dived deeper in tighter shoals. PRI affected the immediate and delayed behavioural changes but not the recovery time. Our study highlights that (1) the behavioural changes of captive European seabass were consistent with previous indoor and outdoor studies; (2) PRI could influence behavioural impact differentially, which may have management implications; (3) some acoustic metrics, e.g. SELcum, may have limited predictive power to assess the strength of behavioural impacts of noise. Noise impact assessments need to consider the contribution of sound temporal structure.

Male bill colour and competition in zebra finches.

Several studies have assessed the role of bill colour in sexual selection and especially with respect to sexual preferences. Even though there are indications that bill colour is related to male quality, so far it has not been shown that bill colour influences male-male interaction. We used male zebra finches with artificially coloured bills in a competitive context to measure the effect of bill colour. In these tests the experimental bird could choose between two feeding sites, each near a stimulus bird with a different bill colour. We tested orange against red, no bird against orange/red and orange/red against green respectively. We found no difference in behaviour towards an orange compared to a red billed stimulus. However the birds spent relatively more time eating when alone compared to being close to a potential competitor. In addition, more time was spent eating than on other behaviours when the birds were close to the orange/red billed stimulus compared to the green billed stimulus. So, although no effect was found in the orange against red test, the results suggest that bill colour may play some role in male-male interaction.

Song learning from playback in zebra finches: is there an effect of operant contingency?

Social interaction is often regarded as crucial for song copying in zebra finches, Taeniopygia guttata. Contingencies in the interaction between pupil and tutor might be essential for the song-copying process. The effect of contingency between a pupil's operant behaviour and tutor song has been studied previously, but with contradictory results. Our aim in this experiment was to provide a more rigorous test of the effect of operant contingent exposure to song playback in zebra finches. Eight experimental males were trained to expose themselves to tutor song by operant key pecking during their sensitive phase for song learning. Each bird had a yoked control, which heard the same tutor song at the same time. All birds were acoustically isolated. The results were surprising in two ways: (1) the control birds copied song to which they were passively exposed; and (2) the experimental birds did not copy more than the controls did. So, we found no effect of operant contingency on song learning. Furthermore, when tested as adults all but one male preferred the tutor song to an unfamiliar one. We conclude that zebra finches can copy playback song, and that social interaction is not crucial for song copying, although it might still be facilitating. Copyright 1999 The Association for the Study of Animal Behaviour.

Perceptual tuning to frequency characteristics of territorial signals in collared doves.

Frequency modulations in the perch coos of collared doves, Streptopelia decaocto, affected the responses of territorial males. In this study we used playback experiments to reveal the impact of absolute and relative aspects of the frequency modulations on this responsiveness. Modulated coos always led to stronger responses compared with unmodulated coos, irrespective of the size of the frequency modulation, except when they contained frequencies outside the natural range. We found an optimum for the size of the frequency modulation, with the strongest responses to coos containing frequency modulations of 75-108 Hz, even though higher modulations are still within the species-specific range. The selective responsiveness shows that territorial males are perceptually tuned to the species-specific frequency range and to the species-specific frequency modulation size. This allows a delineation of the optimal acoustic design of the territorial signal, based on the responsiveness of the receiver. Copyright 1998 The Association for the Study of Animal Behaviour.

Abnormal behavior in caged birds kept as pets.

There are a limited number of studies dealing with abnormal behavior in caged birds kept as pets. However, these studies demonstrate the presence of abnormal behavior in both songbirds and parrots. Ethological studies on these birds, as well as studies on domestic and zoo birds, indicate that inappropriate rearing and housing conditions may lead to behavioral abnormalities. Together these data indicate that behavioral abnormalities occur among both wild-caught and domesticated pet birds. The severity and magnitude of these abnormalities is probably underestimated, and there is a need for systematic studies on the nature, origin, variability, species-specificity, and reversibility of behavioral problems in pet birds. Abnormal behavior in caged birds may to some extent be prevented and reduced by environmental enrichment. However, most enrichment studies are anecdotal and not based on a thorough analysis of the behavioral abnormalities, which may lead to measures resulting in a reduction of symptoms rather than the underlying causes. Although it is likely that several of these problems could be reduced by modifying rearing and housing conditions, the current insights into the causal mechanisms underlying abnormal behavior of domesticated and wild-caught pet birds are limited, as are the insights into the possibilities of preventing or curing abnormal behavior.

Stronger territorial responses to frequency modulated coos in collared doves

Playback experiments were used to investigate the perception of frequency variations in perch coos by collared doves, Streptopelia decaoctoTerritorial males responded more strongly to modulated than to unmodulated coos. This effect was seen whether all three elements of the coo, or just the first element, were modulated. Modulated coos differed from unmodulated coos in two ways, first by an increased average frequency, and second, by the presence of a discrete change in frequency. We show that it was the change in frequency that was responsible for the level of response to modulated coos. The stronger responses to modulated coos are interpreted as a result of the receiver rating the sender as a stronger competitor.Copyright 1997 The Association for the Study of Animal Behaviour1997The Association for the Study of Animal Behaviour

Brood size affects behavior, interclutch interval, LH levels, and weight in ring dove (Streptopelia risoria) breeding pairs.

This study examines the effects of experimental manipulation of brood size (one or two squabs) on the behavior, interclutch interval, plasma LH concentrations, and weights of ring dove parents. Twelve dove pairs were observed, sampled, and weighed over a cycle with one and a cycle with two squabs. Before hatch, no parameter showed any difference between pairs which would subsequently have one or have two squabs. After hatch, males and females having one squab fed less, while males showed more perch-, bow-, and nest-cooing over the 2 weeks after hatch. Females also showed more nest-cooing with one squab and a shorter interclutch interval. For both sexes the plasma LH concentrations were higher when rearing a single squab, showed a lesser decrease after hatch, and increased more rapidly. Both sexes also showed a smaller weight loss when rearing a single squab. The results show that the intricate relationships between behavior, physiology, and reproduction in the ring dove are tuned to brood size and emphasize the latter factor as an important and meaningful variable in the doves' reproductive cycle.

Stimulus representation: a subprocess of imprinting and conditioning.

We suggest a way to reconcile imprinting and associative learning that respects the real differences between the two phenomena but helps to recognize underlying commonalities. Rather than treating each type of learning as the manifestation of a unitary mechanism, we approach learning as a combination of separate subprocesses. Exploration of the literature regarding one of these subprocesses, namely, that governing the representation of stimuli, revealed striking similarities between imprinting and conditioning. These similarities suggest predictions for fresh experimental work that will help to uncover the general rules by which combinations of stimulus features are represented in memory.

Cotransformation and differential expression of introduced genes into potato (Solanum tuberosum L.) cv Bintje.

The Dutch potato cultivar Bintje has been transformed by Agrobacterium strain LBA1060KG, which contains two plasmids carrying three different DNAs (TL- and TR-DNA on the Agrobacterium rhizogenes plasmid and TKG-DNA on the pBI121 plasmid). Several transformed root clones were obtained after transformation of leaf, stem, and tuber segments, and plants were then regenerated from these root clones. The expression of the various marker genes [rol, opine, ß-glucuronidase (GUS), and neomycin phosphotransferase (NPTII)] was determined in several root clones and in regenerated plants. The selection of vigorously growing root clones was as efficient as selection for kanamycin resistance. In spite of the location of NPTII and GUS genes on the same T-DNA, 17% of the root clones did not show GUS activity. Nevertheless, Southern blot analysis showed that these root clones contained at least three copies of the GUS gene. Sixty-four per cent of the root clones contained opines. The expression of these genes, however, was negatively correlated with plant regeneration capacity and normal plant development. The differential expression of the marker genes in the transgenic potato tissues is discussed.

Frequent spontaneous deletions of Ri T-DNA in Agrobacterium rhizogenes transformed potato roots and regenerated plants.

The presence of T-DNA was examined by Southern blot analysis in 16 regenerated shoot lines derived from 6 Agrobacterium rhizogenes-transformed root clones of Solanum tuberosum L. cv. Bintje. TR-DNA, present in regenerated shoot lines from 3 out of 6 root clones was correlated with the presence of opines. One root clone produced opines up to 2.5 years of subculture. However, plant regeneration from and prolonged subculturing of this root clone resulted in loss of opine synthesis, caused by deletion of TR-DNA. TL-DNA inserted at 1 to 5 independent loci was found in 14 of the 16 shoot lines. Surprisingly, 1 to 2 additional insertions next to similar insertions of TL-DNA were found in shoot lines from the same root clone (named 'sister' shoot lines) in 2 out of 4 root clones. Nevertheless, this did not result in gross phenotypic variation between sister shoot lines. Another root clone regenerated 1 shoot line with an Ri phenotype, containing 1 insertion of TL-DNA, and 2 shoot lines with a normal Bintje phenotype without TL-DNA. The 5th root clone showed no difference between sister shoot lines and the 6th root clone produced only 1 shoot line. We conclude that during prolonged root culture and during shoot regeneration from root clones deletion of TL- and TR-DNA insertions can occur. The significance of the frequency of deletion of T-DNA of the Ri plasmid is discussed.

Does behavior contingent stimulus movement enhance filial imprinting in Japanese quail?

Japanese quail chicks were exposed for 2.5 hrs to either a white or a normal stuffed adult conspecific (= model). During this period the model was either nonmoving or it moved for short periods. This movement could be contingent or noncontingent upon distress calls of the chicks. In each condition, exposure led to a significant preference for the familiar model over the nonfamiliar one during a 10-min choice test. Chicks exposed to a nonmoving model had the weakest preference for the familiar model, whereas this preference was strongest in chicks exposed to the contingent moving model; the preference of the chicks exposed to the noncontingent moving model was in between. The results indicate that the extend to which stimulus movement enhances filial imprinting depends on the relation between the chicks behavior and the timing of the stimulus movement. However, it is not clear yet whether the effect arose because the chicks perceived the contingency between the stimulus movement and their behavior or by another mechanism.

The influence of siblings on the development of sexual preferences of male zebra finches.

Broods of young zebra finches were either raised by their own species or cross-fostered by Bengalese finches. Both were isolated visually from other birds at the age of 2 months. Sexual preferences of males were examined at maturity, in a choice between 1 zebra finch female and 1 Bengalese finch female, by measuring the number of song strophes directed at each. Males raised by their own species sang exclusively for the zebra finch female. Cross-fostered males raised without siblings or with only 1 sibling sand exclusively for the Bengalese finch female. A large number of cross-fostered males raised with 2-4 siblings showed at least 5% singing for the zebra finch female, and a small number did so predominantly. It is concluded that under the conditions of these experiments, the development of sexual preferences of zebra finch males is affected by both parental and sibling influences. It is possible that the earlier evidence for a predisposition to response to conspecifics put forward by Immelmann could be explained by hitherto uncontrolled differences in experience.

A rapid method of determining growth characteristics of plant cell populations in batch suspension culture.

A non-destructive, simple and accurate method of determining the relative growth rate (RGR) of the packed cell volume (PCV) of plant suspension cells in one Erlenmeyer flask at any time during the incubation period is described. The Erlenmeyer flask was tilted and the length of the chord formed by the surface of the packed cells across the bottom of the flask was measured. The chord length and the log PCV were correlated in a calibration line. The method enables the RGR during the exponential growth phase to be calculated by multiplying the slope of the linear part of the curve of the chord length in time with the slope of the calibration line. In order to investigate other growth parameters and to analyse the accuracy of the method statistically, a four-parameter function for the chord length and a computer program were used.The RGR during the exponential growth phase of cell suspensions of Solanum tuberosum and Haplopappus gracilis appeared to be independent of the PCV of the inoculum. The method appeared to be sufficiently accurate.