The foraging behaviour of Little Penguins Eudyptula minor at different light levels

The role of vision in the prey-catching behaviour of Little Penguins Eudyptula minor was tested using four captive penguins in a swimming pool. A live fish was placed in the pool with a penguin at various light intensities before and after dawn and dusk. The penguins' behaviour in the morning was the same as in the evening. As the light decreased, the percentage of fish chased by the penguins decreased, and no fish were caught at a light level less than 0.01 μeinstein/m²/s (which occurs approximately 25 min before sunrise and after sunset at latitude 37̀S). The time the penguins spent searching for the fish also decreased with decreasing light. The probability of a penguin pursuing a fish was found to be dependent on the amount of light, such that log,( p /1 - p ) = 6.323 + 2.08 × log,(light level), where p = the probability of pursuing a fish.     

A New Species of Blood Trypanosome from Little Penguins (Eudyptula minor) in Tasmania

ABSTRACT. Trypanosoma eudyptulae n. sp. was present in 9 blood smears from 57 Little Penguins (Eudyptula minor Forster) from Tasmania. Trypanosoma eudyptulae is long and slender (with the kinetoplast situated close to the nucleus) with a long and attenuated posterior end. This is the first report of a trypanosome from a penguin.     

The use of otoliths as indicators of Little Penguin Eudyptula minor diet

The validity of using otoliths from stomach contents quantitatively to determine the number and size of fish consumed was tested on Little Penguins. They were fed different meal sizes of known number and size of fish and the stomach contents were recovered after various time intervals. There were no differences in estimates of original fish size when calculated from otolith length or weight. Rate of digestion of otoliths tended to decrease with increased meal size but increased with time after ingestion. Digestion of otoliths proceeds rapidly and, if ignored, estimates of numbers of fish consumed and of original fish size can be significantly underestimated. This problem can be partially solved by inspection of otolith condition and restricting calculations of fish size to otoliths unaffected by digestion. Many factors introduce variations into rate of otolith degradation and further species-specific studies are required before appropriate correction factors can be applied.     

The use of otoliths as indicators of Little Penguin Eudyptula minor diet

The validity of using otoliths from stomach contents quantitatively to determine the number and size of fish consumed was tested on Little Penguins. They were fed different meal sizes of known number and size of fish and the stomach contents were recovered after various time intervals. There were no differences in estimates of original fish size when calculated from otolith length or weight. Rate of digestion of otoliths tended to decrease with increased meal size but increased with time after ingestion. Digestion of otoliths proceeds rapidly and, if ignored, estimates of numbers of fish consumed and of original fish size can be significantly underestimated. This problem can be partially solved by inspection of otolith condition and restricting calculations of fish size to otoliths unaffected by digestion. Many factors introduce variations into rate of otolith degradation and further species-specific studies are required before appropriate correction factors can be applied.     

Haematology and metabolism of the blood of the little penguin, Eudyptula minor

1. We studied the haematology of the little penguin, Eudyptula minor, and measured red cell enzymes, and the rate of O2 and glucose consumption and CO2 and lactate production of whole penguin blood. 2. Little penguins have a very low RBC count (1.66 x 10(12) l-1) and very large red cells (MCV = 229 microns 3), resulting in a normal haemoglobin and haematocrit. 3. Despite the lower body temperature of penguins, the rate of O2 consumption by whole blood is close to that predicted from studies on other birds.     

Influence of temperature oscillations on some hematological values and metabolism of fish

The reaction of the growth optimum of fish to periodically fluctuating temperature is systemic: there is a synchronous increase in the specific growth rate, reduction of respiration intensity, an increase in red blood cell count and in hemoglobin level, and a decrease in the hemoglobin content in erythrocytes.     

Diving behaviour and energetics in breeding little penguins (Eudyptula minor)

We present data on the diving behaviour and the energetics of breeding little penguins in Tasmania, Australia. Using an 18 m long still water canal in conjunction with respirometry, we determined the energy requirements while diving. Using electronic devices measuring dive depth or swimming speed, we investigated the foraging behaviour at sea. Cost of Transport was calculated to be minimal at the speed the birds prefer at sea (1.8 m/s) and averaged 11.1 J/kg/m (power requirements at that speed: 20.0 W/kg). Metabolic rate of little penguins resting in water was found to be 8.5 W/kg. The externally-attached devices had no significant influence on the energy expenditure.
Foraging trips can be divided into four distinct phases with different diving behaviours. A mean of 500 dives was executed per foraging trip lasting about 18 hours with 60% of this time being spent swimming. The total distance travelled averaged 73 km per day, although foraging range was about 12km. Mean swimming speed of little penguins at sea was 1.8 m/s, maximum swimming speed was 3.3 m/s. More than 50% of all dives had maxima not exceeding 2 m. Maximum depth reached was 27 m. Mean dive duration was 21 s. There were inter-sex differences in diving behaviour as well as changes in foraging behaviour over the breeding period. Aerobic dive limits (ADL) in the wild were estimated between 42 and 50 s. From the swim canal experiments we derived an ADL of 44 s. Total oxygen stores were calculated to be 45 ml O₂/kg. Only 2% of all dives exceeded the ADL. FMRs at sea were calculated to be between 1280 and 1500 kJ/kg/d according to chick size. The yearly food requirements of a breeding little penguin amount to 114 kg.     

Climate fluctuation effects on breeding of blue penguins (Eudyptula minor)

Abstract

El Niño and La Niña climate perturbations alter sea currents and food availability for seabirds in many areas of the world. This changes their breeding success and mortality. Blue penguin (Eudyptula minor) breeding success is dependent upon whether one or two clutches per season are laid, and the hatching and fledging success of these clutches. This study uses six years of data from five blue penguin breeding colonies, three from Taiaroa Head, Otago Peninsula and two from Oamaru, to examine whether annual variation in breeding success correlates with El Niño/La Niña perturbations. When La Niña conditions prevailed, penguins started breeding later, and there was a lower proportion of double breeders than in El Niño and normal years. The probability of a newly hatched chick surviving to fledging was also dependent on whether large‐scale climatic conditions prevailed, whereas hatching success and overall breeding success (number of fledged chicks per breeding pair) showed no correlation with climate perturbations.     

Extending the Functionality of Behavioural Change-Point Analysis with k-Means Clustering: A Case Study with the Little Penguin (Eudyptula minor)

We present a simple framework for classifying mutually exclusive behavioural states within the geospatial lifelines of animals. This method involves use of three sequentially applied statistical procedures: (1) behavioural change point analysis to partition movement trajectories into discrete bouts of same-state behaviours, based on abrupt changes in the spatio-temporal autocorrelation structure of movement parameters; (2) hierarchical multivariate cluster analysis to determine the number of different behavioural states; and (3) k-means clustering to classify inferred bouts of same-state location observations into behavioural modes. We demonstrate application of the method by analysing synthetic trajectories of known ‘artificial behaviours’ comprised of different correlated random walks, as well as real foraging trajectories of little penguins (Eudyptula minor) obtained by global-positioning-system telemetry. Our results show that the modelling procedure correctly classified 92.5% of all individual location observations in the synthetic trajectories, demonstrating reasonable ability to successfully discriminate behavioural modes. Most individual little penguins were found to exhibit three unique behavioural states (resting, commuting/active searching, area-restricted foraging), with variation in the timing and locations of observations apparently related to ambient light, bathymetry, and proximity to coastlines and river mouths. Addition of k-means clustering extends the utility of behavioural change point analysis, by providing a simple means through which the behaviours inferred for the location observations comprising individual movement trajectories can be objectively classified.     

Acoustic properties of male advertisement and their impact on female responsiveness in little penguins Eudyptula minor

We examined the relationship between acoustic properties of male advertising calls, male body size and female responses in little penguins Eudyptula minor . Larger males produced calls of lower frequency. Playback experiments indicated that females were more likely to respond to low or medium pitched calls, than to high ones (although only 28% of females responded vocally to playback). This may reflect the interest of unmated females in large to medium sized senders as potential mates, or indicate a stronger territorial response to large intruders.     

Foraging behaviour of the little penguin, Eudyptula minor: initial results and assessment of instrument effect

We investigated the foraging behaviour of little penguins using a new archival electronic activity recorder which simultaneously measures speed and depth against time. We present the first integrated data of foraging behaviour of two little penguins, from which we were able to distinguish between several types of travelling and foraging behaviours. The little penguins foraged mainly within 15 m of the surface and travelled at speeds between 8 and 9 km h^-1. Using attachments ranging between 1.4 and 11.8% penguin cross-sectional area (0.1 and 6% penguin mass), and isotopic water, we also assessed the effects of carrying devices while foraging. Both water influx and metabolic rates were significantly lower in penguins carrying devices, compared to penguins foraging without devices attached. Even the relatively small attachments resulted in a decreased foraging efficiency and we suggest that there is no simple or fixed relationship between size of device and the effect on the bearer.     

Blue penguin (Eudyptula minor) nest distribution and breeding success on Otago Peninsula, 1992 to 1998

Abstract

Annual counts of nests with eggs or chicks (known nests) were made at blue penguin (Eudyptula minor) breeding sites on the Otago Peninsula in each November from 1994 to 1997. Although the population has doubled to an estimated 600 known nests over this period, the number of breeding sites on the Otago Peninsula has reduced since the 1970s. Breeding success at three areas at Taiaroa Head were monitored by regular nest checks in the breeding season from 1992 to 1998. At Taiaroa Head reproductive success ranged from 41 to 78% at the three sites during the seven‐year study and was generally higher for pairs nesting in nest boxes than for those in burrows. The percentage of breeding pairs that laid a second clutch after fledging at least one chick from their first clutch (double brooded) varied between seasons (0–48%) and was correlated with the date of the onset of breeding. Egg loss, possibly through predation by Norway rats (Rattus norvegicus), influenced the significantly lower reproductive success at one area (Area A) at Taiaroa Head during the 1996 season.     

Reproductive performance of little penguins Eudyptula minor in relation to year, age, pair-bond duration, breeding date and individual quality

We measured breeding performance of little penguins Eudyptula minor at Phillip Island, Victoria, Australia, during a 21-year period. All birds considered in this paper (n=307) were of known age (2–22 y) and sex, and most were of known, or closely-estimated, pair-bond status (1–8 mates per bird; pair-bond durations 1–13 y). Breeding dates and breeding performance varied markedly from year to year; measures of annual performance were not associated with early breeding. Measures of individual breeding performance (clutch-size, hatching success, chick masses and productivity) were related to early laying, parental age, and duration of pair-bond. Dependence of breeding performance on parental age was curvilinear, levelling off at about 8 y of age. Productivity declined significantly among birds older than 8 y; this decline was not due to events in the last year of breeding ("terminal illness"). Breeding performance increased with duration of pair-bond at least through y 5. Early breeding was significantly related to age and duration of pair-bond. Most of these relationships were stronger among males than among females, and many of them were not significant when females were considered alone. After controlling for other factors, breeding performance varied significantly among birds, but autocorrelations were low and limited to intervals of one year. Parental quality (defined for birds studied in six or more years as the individual bird term in a GLM for productivity controlling for other factors) was not correlated with lifespan or other demographic parameters, but high-quality birds were less prone to change mates and burrows than low-quality birds. We know of no previous study in which simultaneous effects of laying date, age and pair-bond duration on breeding performance were measured, while controlling for year, individual quality and terminal illness.     

Assessment of flora diversity in a minor river valley using ecological indicator values, Geographical Information Systems and Digital Elevation Models

Ellenberg indicator values (EIV) have been widely used to estimate habitat variables from floristic data and to predict vegetation composition based on habitat properties. Geographical Information Systems (GIS) and Digital Elevation Models (DEM) are valuable tools for studying the relationships between topographic and ecological characters of river systems. A 3-meter resolution DEM was derived for a. 3-km-long break section of the Szum River (SE Poland) from a 1:10,000 topographic map. Data on the diversity and ecological requirements of the local vascular flora were obtained while making floristic charts for 32 sections of the river valley (each 200 m long) and physical and chemical soil measurements; next, the data were translated into EIV. The correlations of the primary and secondary topographic attributes of the valley, species richness, and EIV (adapted for the Polish vascular flora) were assessed for all species recognized in each valley section. The total area and proportion of a flat area, mean slope, slope curvature, solar radiation (SRAD), and topographic wetness index (TWI) are the most important factors influencing local flora richness and diversity. The highest correlations were found for three ecological indicators, namely light, soil moisture, and soil organic content. The DEM seems to be useful in determination of correlations between topographic and ecological attributes along a minor river valley.     

Comparison of barometric and pneumotachographic measurements of resting ventilation in the little penguin (Eudyptula minor)

1. We compared the use of the barometric method and pneumotachography for measurement of ventilation in the little penguin Eudyptula minor. 2. Simultaneous use of both techniques showed the barometric method to give a reliable estimate of tidal volume. 3. Comparison of birds with and without masks for pneumotachography showed wearing masks to produce a significant increase in ventilation, principally through a raised respiratory frequency.     

生态因子的波动对多刺裸腹溞雄体发生的影响

采用克隆培养法,研究了几种主要生态因子的波动对多刺裸腹氵蚤雄体发生的影响和该氵蚤对上述生态因子波动的敏感程度.结果表明,无论是一次性剧烈刺激,还是持续性渐进刺激,该氵蚤均未能直接产生雄体,即氵蚤的孤雌生殖雌体不能直接转变为混交雌体(两性生殖雌体);在光照、温度、饵料密度、pH值持续性渐进波动时,该氵蚤种群的内禀增长率分别为0.7748、0.7481、0.6539和0.6310d-1ind-1,比对照组降低0.9%、4.0%、16.4%和19.3%,表明该氵蚤对饵料密度和pH值的波动较为敏感,对温度的敏感性次之     

Population trends in a substantial colony of Little Penguins: three independent measures over three decades

Estimating long-term population trends is vital for the conservation and management of species, yet few trends exist and fewer still are verified with independent measures. We compared three independent measures of change in population size over 27 years (1984–2011) for a significant Little Penguin Eudyptula minor colony in south-eastern Australia: (1) a series of 13 colony-wide surveys conducted in eight separate years, (2) mean nightly counts of penguins returning to breeding sites (365 counts × 27 years) and (3) population growth rates from a demographic model based on survival and recruitment rates measured at three sites each year. Colony-wide surveys of burrows were used as a benchmark of change in population size in the 8 years they were conducted as they were a robust measure of population size corrected for intra-annual variation in burrow occupancy using mark-recapture modelling at six reference sites. However, the demographic model matched the trend from colony-wide surveys with greater resolution in years and with less effort. Beach counts were unreliable for monitoring trends for the entire population due to its singular and peripheral location in the colony. Trends indicate a doubling of the population from 1984 to 2011 despite a marked population contraction linked to a mass mortality of a key prey species. The colony appears secure but remains subject to changes in the marine and terrestrial environments in the longer term.