Behaviour

Parker, G.A.

doi: 10.1163/156853974X00327pmid: N/A

<jats:sec><jats:title>Abstract</jats:title><jats:p>Time investment strategy is defined as the optimum allocation of times spent on given activities so as to achieve maximum reproductive success. Selective pressures on males to increase time invested in encountering females would be least in sessile and communally spawning species, and maximum in mobile species which spawn at low density and those which copulate. The present paper concerns male time investment in courtship persistence and female-guarding. Staying with a given female reduces the rate at which new females are encountered. Females are often unreceptive for some time after mating. Males often court unreceptive conspecific females; they can achieve a gain if the female rejection reactions can be overcome (rape) and the ejaculate can compete in the fertilization of the ova. Courtship of unreceptive females of closely related sympatric species is also considered adaptive. Though female unreceptivity will be favoured if hybrids are disadvantageous, males may gain by attempting rape if the fitness of hybrid offspring is high enough and the time investment favourable. A model is constructed to explain how optimum persistence durations are determined. This depends on 1) how the cumulative probability of insemination changes through time invested, 2) the encounter frequency, 3) the ejaculate cost (measured as feeding time investment/ejaculate), and 4) is modified by the pattern of gain from other types of female. Females can adapt to male persistence either by acceptance, by increasing rejection effectiveness, or by dispersing into another area where it is disadvantageous for males to search. This last solution may have been especially important in sympatric speciation. Male courtship duration with potentially receptive conspecific females may also be optimized. Variation in male persistence time may be due to assessment of particular situations. Female guarding has commonly evolved as a male time investment strategy. Precopulatory guarding appears to function to stake a claim to a female (or females) until she becomes receptive. This poses two problems : at what point in the female's reproductive life does it become advantageous for the male to guard, and how is guarding time optimized? Optimum guarding duration can be determined with the same model as for courtship persistence. If males adopt a given cue for closeness to receptivity for the onset of guarding, females showing the cue become scarce and selection may favour drive for earlier and earlier cues. This could be stabilized by the opposing selective pressures of 1) chances of finding a female closer to mating high enough, 2) female distribution suitably non-random with respect to mating, and 3) guarding investment more costly than searching investment in terms of male future reproductive success. Postcopulatory guarding appears to function to prevent loss in gain to a male due to sperm competition from other males. Such behaviour could evolve in conditions of high female receptivity and high encounter rate during an adequate overlap period (time per female during which ejaculates from different males can compete for fertilization of the ova), since males which guard after mating may waste less time and sperm than non-guarders. Its advantage is increased by a male-biassed sex ratio during the overlap period. The behaviour depends on the fact that second matings can compete in the fertilization of the ova, and postcopulatory guarding has its higlest advantage when the last male to mate fertilizes most eggs. Optimum guarding duration can be determined with basically the same model as before, and depends mainly on how sperm utilization is distributed within the overlap period.</jats:p> </jats:sec>

Parker, G.A.

doi: 10.1163/156853974x00327pmid: N/A

AbstractTime investment strategy is defined as the optimum allocation of times spent on given activities so as to achieve maximum reproductive success. Selective pressures on males to increase time invested in encountering females would be least in sessile and communally spawning species, and maximum in mobile species which spawn at low density and those which copulate. The present paper concerns male time investment in courtship persistence and female-guarding. Staying with a given female reduces the rate at which new females are encountered. Females are often unreceptive for some time after mating. Males often court unreceptive conspecific females; they can achieve a gain if the female rejection reactions can be overcome (rape) and the ejaculate can compete in the fertilization of the ova. Courtship of unreceptive females of closely related sympatric species is also considered adaptive. Though female unreceptivity will be favoured if hybrids are disadvantageous, males may gain by attempting rape if the fitness of hybrid offspring is high enough and the time investment favourable. A model is constructed to explain how optimum persistence durations are determined. This depends on 1) how the cumulative probability of insemination changes through time invested, 2) the encounter frequency, 3) the ejaculate cost (measured as feeding time investment/ejaculate), and 4) is modified by the pattern of gain from other types of female. Females can adapt to male persistence either by acceptance, by increasing rejection effectiveness, or by dispersing into another area where it is disadvantageous for males to search. This last solution may have been especially important in sympatric speciation. Male courtship duration with potentially receptive conspecific females may also be optimized. Variation in male persistence time may be due to assessment of particular situations. Female guarding has commonly evolved as a male time investment strategy. Precopulatory guarding appears to function to stake a claim to a female (or females) until she becomes receptive. This poses two problems : at what point in the female's reproductive life does it become advantageous for the male to guard, and how is guarding time optimized? Optimum guarding duration can be determined with the same model as for courtship persistence. If males adopt a given cue for closeness to receptivity for the onset of guarding, females showing the cue become scarce and selection may favour drive for earlier and earlier cues. This could be stabilized by the opposing selective pressures of 1) chances of finding a female closer to mating high enough, 2) female distribution suitably non-random with respect to mating, and 3) guarding investment more costly than searching investment in terms of male future reproductive success. Postcopulatory guarding appears to function to prevent loss in gain to a male due to sperm competition from other males. Such behaviour could evolve in conditions of high female receptivity and high encounter rate during an adequate overlap period (time per female during which ejaculates from different males can compete for fertilization of the ova), since males which guard after mating may waste less time and sperm than non-guarders. Its advantage is increased by a male-biassed sex ratio during the overlap period. The behaviour depends on the fact that second matings can compete in the fertilization of the ova, and postcopulatory guarding has its higlest advantage when the last male to mate fertilizes most eggs. Optimum guarding duration can be determined with basically the same model as before, and depends mainly on how sperm utilization is distributed within the overlap period.

Liley, N.R.; Wishlow, W.

doi: 10.1163/156853974X00336pmid: 4817518

<jats:sec><jats:title>Abstract</jats:title><jats:p>1. A large proportion of virgin female guppies, Poecilia reticulata, are highly responsive when first placed with actively courting males. This responsiveness wanes over several days if a female is repeatedly exposed to male courtship in a standard test situation (15 mins./day on alternate days). The decline in response occurs even though copulation is prevented by presenting males which have been gonopodectomized (gonopodium removed). Many females become responsive again for a short period(s) some time after the initial period of receptivity at the start of testing. Examination of individual records of females tested for up to 6 weeks suggests that there are cycles in responsiveness which correspond closely to the 20-21 day cycle in receptivity demonstrated in nonvirgin fish (Liley, 1966). The data indicate that a virgin female is likely to be initially highly responsive whatever the stage of her endogenous cycle, hut after involvement in courtship a cycle in responsiveness becomes apparent. 2. Naive virgin females were highly responsive when first tested 2, 10 or 24 days after ovariectomy (Experiment 2). However in contrast to intact fish there was no reappearance of receptive behaviour after sexual activity observed at the start of testing had waned. 3. The rate of decline in responsiveness of naive virgin females is to some extent dependent upon the courtship testing regime (Experiment 3). Most females tested with gonopodectomized males for 20 minutes per day had become unresponsive by the 6th or 7th day; receptivity of females tested at 3 and 6 day intervals declined more slowly but eventually reached the same level as fish tested every day. Testing females with intact males on the first three days resulted in a more rapid drop in female responsiveness. Ovariectomized females were less responsive and their receptively waned more rapidly than intact females. 4. In experiment 4, an attempt was made to determine whether the high initial responsiveness of virgin females was due to the fact that they had been deprived of social stimulation provided by males. Virgin females were tested with gonopodectomized males on 8 consecutive days during which their receptivity declined to a low level. Females were then isolated from males individually or in groups for 1, 2, 3, 4 or 6 weeks before being retested with gonopodectomized males. There was no recovery of responsiveness to a level typical of naive virgin fish in the previously isolated females. Any recovery of responsiveness which did occur was that which might be expected on the basis of each female having the potential to undergo a cycle in receptivity related to an endogenous cycle of approximately 20 days. 5. It is concluded that there is a cycle in receptivity in virgin females which reflects an endocrine cycle in ovarian activity. In addition naive fish show an initially high level of response which is not dependent on the immediate ovarian hormone state and masks the cycle regulated by the ovary. The responsiveness of naive fish habituates as a result of exposure to male courtship. It is suggested that the interaction between the decremental effects (habituation) induced by courtship and the incremental effects of ovarian hormone and short-term incremental effects of courtship may interact in a manner which adjust female receptivity to the social environment, terminating sexual responsiveness once insemination has occurred a number of times.</jats:p> </jats:sec>

Liley, N.R.; Wishlow, W.

doi: 10.1163/156853974x00336pmid: 4817518

Abstract1. A large proportion of virgin female guppies, Poecilia reticulata, are highly responsive when first placed with actively courting males. This responsiveness wanes over several days if a female is repeatedly exposed to male courtship in a standard test situation (15 mins./day on alternate days). The decline in response occurs even though copulation is prevented by presenting males which have been gonopodectomized (gonopodium removed). Many females become responsive again for a short period(s) some time after the initial period of receptivity at the start of testing. Examination of individual records of females tested for up to 6 weeks suggests that there are cycles in responsiveness which correspond closely to the 20-21 day cycle in receptivity demonstrated in nonvirgin fish (Liley, 1966). The data indicate that a virgin female is likely to be initially highly responsive whatever the stage of her endogenous cycle, hut after involvement in courtship a cycle in responsiveness becomes apparent. 2. Naive virgin females were highly responsive when first tested 2, 10 or 24 days after ovariectomy (Experiment 2). However in contrast to intact fish there was no reappearance of receptive behaviour after sexual activity observed at the start of testing had waned. 3. The rate of decline in responsiveness of naive virgin females is to some extent dependent upon the courtship testing regime (Experiment 3). Most females tested with gonopodectomized males for 20 minutes per day had become unresponsive by the 6th or 7th day; receptivity of females tested at 3 and 6 day intervals declined more slowly but eventually reached the same level as fish tested every day. Testing females with intact males on the first three days resulted in a more rapid drop in female responsiveness. Ovariectomized females were less responsive and their receptively waned more rapidly than intact females. 4. In experiment 4, an attempt was made to determine whether the high initial responsiveness of virgin females was due to the fact that they had been deprived of social stimulation provided by males. Virgin females were tested with gonopodectomized males on 8 consecutive days during which their receptivity declined to a low level. Females were then isolated from males individually or in groups for 1, 2, 3, 4 or 6 weeks before being retested with gonopodectomized males. There was no recovery of responsiveness to a level typical of naive virgin fish in the previously isolated females. Any recovery of responsiveness which did occur was that which might be expected on the basis of each female having the potential to undergo a cycle in receptivity related to an endogenous cycle of approximately 20 days. 5. It is concluded that there is a cycle in receptivity in virgin females which reflects an endocrine cycle in ovarian activity. In addition naive fish show an initially high level of response which is not dependent on the immediate ovarian hormone state and masks the cycle regulated by the ovary. The responsiveness of naive fish habituates as a result of exposure to male courtship. It is suggested that the interaction between the decremental effects (habituation) induced by courtship and the incremental effects of ovarian hormone and short-term incremental effects of courtship may interact in a manner which adjust female receptivity to the social environment, terminating sexual responsiveness once insemination has occurred a number of times.

Jarman, P.J.

doi: 10.1163/156853974x00345pmid: N/A

AbstractThe types of social organisation displayed by the African antelope species have been assigned in this paper to five classes, distinguished largely by the strategies used by the reproductively active males in securing mating rights, and the effects of those strategies on other social castes. The paper attempts to show that these strategies are appropriate to each class because of the effects of other, ecological, aspects of their ways of life. The paper describes different feeding styles among antelope, in terms of selection of food items and coverage of home ranges. It argues that these feeding styles bear a relationship to maximum group size of feeding animals through the influence of dispersion of food items upon group cohesion. The feeding styles also bear a relationship to body size and to habitat choice, both of which influence the antelope species' antipredator behaviour. Thus feeding style is related to anti-predator behaviour which, in many species, influences minimum group size. Group size and the pattern of movement over the annual home range affect the likelihood of females being found in a given place at a given time, and it is this likelihood which, to a large extent, determines the kind of strategy a male must employ to achieve mating rights. The effects of the different strategies employed by males can be seen in such aspects of each species' biology as sexual dimorphism, adult sex ratio, and differential distribution of the sexes.

Jarman, P.J.

doi: 10.1163/156853974X00345pmid: N/A

<jats:sec><jats:title>Abstract</jats:title><jats:p>The types of social organisation displayed by the African antelope species have been assigned in this paper to five classes, distinguished largely by the strategies used by the reproductively active males in securing mating rights, and the effects of those strategies on other social castes. The paper attempts to show that these strategies are appropriate to each class because of the effects of other, ecological, aspects of their ways of life. The paper describes different feeding styles among antelope, in terms of selection of food items and coverage of home ranges. It argues that these feeding styles bear a relationship to maximum group size of feeding animals through the influence of dispersion of food items upon group cohesion. The feeding styles also bear a relationship to body size and to habitat choice, both of which influence the antelope species' antipredator behaviour. Thus feeding style is related to anti-predator behaviour which, in many species, influences minimum group size. Group size and the pattern of movement over the annual home range affect the likelihood of females being found in a given place at a given time, and it is this likelihood which, to a large extent, determines the kind of strategy a male must employ to achieve mating rights. The effects of the different strategies employed by males can be seen in such aspects of each species' biology as sexual dimorphism, adult sex ratio, and differential distribution of the sexes.</jats:p> </jats:sec>

Fernald, Russell D.; Heinecke, Peter

doi: 10.1163/156853974X00354pmid: N/A

<jats:sec><jats:title>Abstract</jats:title><jats:p>We describe a multi-mode event recorder for registering behavioral events directly on a punched paper tape. The paper tape produced can be read by any computer equipped with a paper tape reader. For paper tape with an 8-bit code, 256 different events can be registered. The device itself can be operated in any one of four modes. In the first mode, pressing a key on the keyboard results in a unique code (hole combination) being punched on the paper tape. In the second mode of operation, a sequentially increasing number ("time") is punched automatically at preset intervals. In addition, other codes may be entered via the keyboard. A time punch may thus be used to signal that an observation should be entered from the keyboard. In the third mode, the machine punches, at regular intervals, the code of the key currently depressed. In mode 4, external events are counted for a given time interval and the sum punched onto the tape at the end of the interval. With each punch, the sum is reset to zero. The paper tapes produced are read directly and the data processed according to the program. This results in a great reduction in the time necessary to process data. The system is compared with other devices which use magnetic tape as an intermediate storage device. The main advantage of this system is the time saved in processing data.</jats:p> </jats:sec>

Fernald, Russell D.; Heinecke, Peter

doi: 10.1163/156853974x00354pmid: N/A

AbstractWe describe a multi-mode event recorder for registering behavioral events directly on a punched paper tape. The paper tape produced can be read by any computer equipped with a paper tape reader. For paper tape with an 8-bit code, 256 different events can be registered. The device itself can be operated in any one of four modes. In the first mode, pressing a key on the keyboard results in a unique code (hole combination) being punched on the paper tape. In the second mode of operation, a sequentially increasing number ("time") is punched automatically at preset intervals. In addition, other codes may be entered via the keyboard. A time punch may thus be used to signal that an observation should be entered from the keyboard. In the third mode, the machine punches, at regular intervals, the code of the key currently depressed. In mode 4, external events are counted for a given time interval and the sum punched onto the tape at the end of the interval. With each punch, the sum is reset to zero. The paper tapes produced are read directly and the data processed according to the program. This results in a great reduction in the time necessary to process data. The system is compared with other devices which use magnetic tape as an intermediate storage device. The main advantage of this system is the time saved in processing data.

Smith, James N.M.

doi: 10.1163/156853974X00363pmid: N/A

<jats:sec><jats:title>Abstract</jats:title><jats:p>1. The movement path of a predator will clearly be an important determinant of its ability to encounter and subsequently attack suitable prey items. Previous work on this aspect of searching behaviour has been mainly carried out on invertebrates, while this study describes the movement paths of two bird predators, the european blackbird and the song thrush (collectively referred to as 'thrushes') on a grass meadow in central Oxford. 2. The paths of foraging thrushes are divided up into natural units consisting of a series of alternating moves and pauses. A method of mapping these moves is presented (Figs 2, 3). 3. The large scale movements of the thrushes on the meadow was not uniform and this was probably related to non-uniformity in the environment, possibly including factors influencing feeding success (Figs 4, 6). 4. The durations of the moves and pauses were measured from cine film and video tape records. Only between one sixth and one tenth of the total foraging time was spent in actual movement, the remainder probably being spent largely in scanning for, or attacking, potential prey objects (Figs 7, 8). 5. Measures of the individual move lengths and angles. turned between successive moves were taken from the maps (Figs 3, 9), and the average speeds of movement were calculated for each track. Song thrushes and female blackbirds made longer moves than male blackbirds, and female blackbirds moved across the meadow at a higher overall speed than male blackbirds or song thrushes (Tables 1-4). 6. Methods are presented for describing the 'rules of movement' of the thrushes across the study meadow. When feeding mainly on earthworms, thrushes tended to make sequences of three, or possibly more, moves that were similar in length, and to make pairs, triplets, and possibly bigger groupings of alternating left and right turns. The size of each move was independent of the sign of the preceding turn and vice versa. The tendency of successive turns to alternate in sign, combined with the relatively restricted size of turns between moves, produced an ongoing search path, thus avoiding the pitfall of searching the same ground twice in a short time.</jats:p> </jats:sec>

Smith, James N.M.

doi: 10.1163/156853974x00363pmid: N/A

Abstract1. The movement path of a predator will clearly be an important determinant of its ability to encounter and subsequently attack suitable prey items. Previous work on this aspect of searching behaviour has been mainly carried out on invertebrates, while this study describes the movement paths of two bird predators, the european blackbird and the song thrush (collectively referred to as 'thrushes') on a grass meadow in central Oxford. 2. The paths of foraging thrushes are divided up into natural units consisting of a series of alternating moves and pauses. A method of mapping these moves is presented (Figs 2, 3). 3. The large scale movements of the thrushes on the meadow was not uniform and this was probably related to non-uniformity in the environment, possibly including factors influencing feeding success (Figs 4, 6). 4. The durations of the moves and pauses were measured from cine film and video tape records. Only between one sixth and one tenth of the total foraging time was spent in actual movement, the remainder probably being spent largely in scanning for, or attacking, potential prey objects (Figs 7, 8). 5. Measures of the individual move lengths and angles. turned between successive moves were taken from the maps (Figs 3, 9), and the average speeds of movement were calculated for each track. Song thrushes and female blackbirds made longer moves than male blackbirds, and female blackbirds moved across the meadow at a higher overall speed than male blackbirds or song thrushes (Tables 1-4). 6. Methods are presented for describing the 'rules of movement' of the thrushes across the study meadow. When feeding mainly on earthworms, thrushes tended to make sequences of three, or possibly more, moves that were similar in length, and to make pairs, triplets, and possibly bigger groupings of alternating left and right turns. The size of each move was independent of the sign of the preceding turn and vice versa. The tendency of successive turns to alternate in sign, combined with the relatively restricted size of turns between moves, produced an ongoing search path, thus avoiding the pitfall of searching the same ground twice in a short time.