Bright Nights Research Articles

Habitat choice and vigilance behaviour of brush-tailed rock-wallabies (Petrogale penicillata) within their nocturnal foraging ranges

Habitat choice by brush-tailed rock-wallabies (Petrogale penicillata) in south-east Queensland was investigated by comparing the attributes of the nocturnal foraging locations that they selected with those of random locations within a radius of 50 m. Brush-tailed rock-wallabies were shown to select foraging locations on the basis of forage quality and/or their ability to see predators, rather than protection from predators amongst vegetation that could conceal them. Habitat choice may have been affected by limited food availability, as this study was conducted in the winter dry season. The attributes of foraging locations that brush-tailed rock-wallabies perceived as increasing their predation risk were assessed by recording the proportion of time that brush-tailed rock-wallabies spent vigilant while foraging. To measure vigilance, focal animals were observed with a night-vision scope for two minutes and the proportions of time spent vigilant and feeding were recorded. No measured feature of foraging locations was related to higher vigilance levels, suggesting that brush-tailed rock-wallabies did not alter their vigilance whether sheltered amongst grass tussocks or in open habitat, or whether feeding on good quality or poorer quality vegetation. Vigilance levels significantly declined as overnight temperatures decreased, which may have resulted from higher energy requirements of brush-tailed rock-wallabies during winter. The only factors that were found to significantly increase vigilance levels were high winds and moonlit nights. On bright nights, brush-tailed rock-wallabies were very unsettled and during high winds they often did not emerge to feed. More information is needed about how macropods detect predators at night before the effects of wind and light intensity upon vigilance can be fully understood.

Predation risk and moonlight avoidance in nocturnal seabirds

Unlike most seabird families, the vast majority of small petrel species are nocturnal on their breeding grounds. Further, they reduce markedly their activity when the light level increases. Moonlight avoidance might be a consequence of reduction in foraging profitability, as bioluminescent prey do not come to the sea surface on bright nights. Alternatively, petrels may avoid colonies during moonlit nights because of increased predation risk. We studied predation on petrels by Brown Skuas Catharacta antarctica lönnbergi at Kerguelen, and the influence of moonlight on behaviour of both skuas and petrels, to test the ‘predation risk’ hypothesis. On the study area, Brown Skuas hunt at night and prey heavily upon the Blue Petrel Halobaena caerulea and the Thin‐billed Prion Pachyptila belcheri. Predation risk was higher on moonlit nights, as skuas caught more prey, and particularly more Blue Petrels when the light level increased. Nightly intakes of Blue Petrel and Thin‐billed Prion by skuas was related to colony attendance of non‐breeders rather than that of breeders. Biometry of prey also suggested that skuas caught a higher proportion of non‐breeding birds than was present at the colonies. Predation risk was thus greater in non‐breeders and on moonlit nights. Colony attendance by non‐breeding Blue Petrels and Thin‐billed Prions was also reduced during moonlit nights. Vocal activity, which is mainly by non‐breeders, was also drastically reduced when the light level increased in the species suffering the highest predation rate. Our results supported the ‘predation risk’ hypothesis, although the ‘foraging efficiency’ and the ‘predation risk’ hypotheses are not mutually exclusive: the former might explain the moonlight avoidance behaviour of breeding, and the latter that of non‐breeding individuals.

Lunar synchrony in the reproduction of the Moluccan Megapode Megapodius wallacei

The Moluccan Megapode Megapodius wallacei uses heat generated by the sun to incubate its eggs. It buries the eggs deep in the sand of sun‐exposed beaches and open sandy areas on islands in the Moluccas, Indonesia. The eggs are laid at night and left to incubate for two to three months without parental care. We present evidence that the Moluccan Megapode exhibits lunar synchrony in the timing of egg‐laying, its spatial distribution of egg burrows and in its behaviour at communal nesting grounds. More Moluccan Megapodes visit the nesting grounds on bright nights than during the new moon. Data collected on the spatial distribution and depth of egg burrows also exhibit lunar periodicity. On moonlit nights, the birds excavate burrows in communal groups and spend longer at the nesting ground digging deeper burrows. Lunaphilia and lunar periodicity of reproduction are rarely documented in birds. We discuss possible explanations for these behaviours in the Moluccan Megapode.

Does Moonlight Change Vertical Stratification of Activity by Forest-Dwelling Insectivorous Bats?

We hypothesized that bats would not change total nightly activity in response to the lunar cycle but would exhibit a shift in habitat among vertical levels (different degrees of spatial complexity and light penetration) of temperate rainforest with changing levels of lunar light. As predicted, we found no evidence that activity of bats varied directly with intensity of moonlight. However, activity changed depending on height within the forest, and there was a significant interaction between moonlight and height. The shift between vertical levels was not expected if risk of predation was an important selective pressure, because activity was highest in the canopy and lowest at the level of shrubs on bright nights. The most likely explanation for interaction between height and moonlight is that bats adjust use of microhabitats to match distribution of prey.

Were Noctilucent Clouds Caused by the Krakatoa Eruption? A Case Study of the Research Problems before 1885

It is known that noctilucent clouds were first observed in 1885, two years after the great Krakatoa eruption in the Sunda Straits. The preeminent question of whether noctilucent clouds appeared before 1885 is studied here in detail. Using various literature sources and observational records for the nineteenth century from several observers it can be shown that before 1885 noctilucent clouds were never described in the literature. The so-called bright nights or Leuchtstreifen phenomenon was well known in the nineteenth century, but no observer described any structures that can be identified as noctilucent clouds. This result makes it clear that the noctilucent clouds seen in 1885 were the first such observations to be made. A possible increase in frequency of occurrence can be estimated from the year of discovery up to the present day.

The effects of moonlight on nocturnal activity in bushy-tailed wood rats (Neotoma cinerea)

The nocturnal activity of bushy-tailed wood rats (Neotoma cinerea) was monitored for two breeding seasons (1993 and 1994) in the Canadian Rockies. Radiotelemetry was used under three levels of moonlight to assess two measures of nocturnal activity: (i) the proportion of animals crossing rocky outcrops and entering the surrounding forest to forage, search for mates, or both, and (ii) the distance moved from the den site while in the forest. Males and females exhibited significant differences among moonlight levels, with greater activity on nights of intermediate-level moonlight and less activity on nights with bright or dark moonlight. There was no difference in the proportions of males and females active at any moonlight level. The distances moved from the den did not differ among moonlight levels for either males or females. Having traversed the rocks and entered the forest, individuals moved similar distances regardless of light level. These results suggest that wood rats respond to moonlight only when making the decision to cross rocks and enter the forest. This behaviour presumably serves to counteract the increased risk of predation on bright nights.

Global Change in the Mesosphere and the Question of the Appearance of Noctilucent Clouds Before 1885

It is known that noctilucent clouds were first observed in 1885, two years after the great Krakatoa eruption in the Sunda Straits. The pre-eminent question whether noctilucent clouds appeared before 1885 is here studied in detail. Using various literature sources and observational records for the 19th century by several observers it can be shown that before 1885 noctilucent clouds were never described in the literature. The so-called phenomenon “bright nights” or “Leuchtstreifen” was well-known in the 19th century, but no observer described any structures which can be identified as noctilucent clouds. This result makes it clear that the noctilucent clouds seen in 1885 were the first such observations made. A possible increase in frequency of occurrence can be estimated from the year of discovery up to the present day.

Use of Simulated Herbaceous Canopy by Foraging Rodents

-Use of seeds from simulated herbaceous canopy by western harvest mice (Reithrodontomys megalotis), deer mice (Peromyscus maniculatus) and white-footed mice (Permyscus leucopus) was examined in laboratory trials. Each mouse was tested on both simulated full-moon and new-moon nights but with only one of three abundances of surface seeds (high, low or zero abundances of seeds in trays on arena floor). White-footed mice ate more total seeds (surface plus canopy seeds) during dark-bright than bright-dark trials and with high than low or zero abundances of surface seeds. However, neither the order of dark and bright conditions nor availability of surface seeds influenced total seeds eaten by deer mice and harvest mice. All three species readily foraged in the canopy in the absence of surface seeds (>90% of trials on both dark and bright nights). When surface seeds were abundant, interspecific differences in canopy foraging were evident as canopy foraging occurred during 54% of trials on both dark and bright nights for harvest mice, 58% and 21% of trials on dark and bright nights, respectively, for white-footed mice and 8% and 0% of trials on dark and bright nights for deer mice.

Assessment of predation risk via illumination level: facultative central place foraging in the cricetid rodent Phyllotis darwini

It is well known that the risk of predation affects prey decision making. However, few studies have been concerned with the cues used by prey to assess this risk. Prey animals may use indirect environmental cues to assess predation hazard since direct evaluation may be dangerous. I studied the assessment of predation risk, manipulated via environmental illumination level, and the trade-off between foraging and predation hazard avoidance in the nocturnal rodent Phyllotis darwini (Rodentia: Cricetidae). In experimental arenas I simulated dark and full moon nights (which in nature correlate with low and high predation risk, respectively) and measured the immediate responses of animals to flyovers of a raptor model. Second, varying illumination only, I evaluated patch use, food consumption, central place foraging, and nocturnal variation of body weight. During flyover experiments, animals showed significantly more evasive reactions under full moon illumination than in moonless conditions. In the patch use experiments, rodents significantly increased their giving-up density and decreased their total food consumption under moonlight. On dark nights, rodents normally fed in the food patch, but when illumination was high they became central place foragers in large proportion. Moreover, the body weight of individuals decreased proportionately more during bright nights. These results strongly suggest that P. darwini uses the level of environmental illumination as a cue to the risk of being preyed upon and may sacrifice part of its energy return to avoid risky situations.

Population dynamics and habitat use of the long-haired rat (Rattus villosissimus) in south-western Queensland

A population of Rattus villosissimus was studied during an 18-month period in a sand-dune habitat in south-western Queensland. The population numbers fluctuated dramatically during this time. Increases in population numbers were due primarily to immigration, with reproduction playing a secondary role. Rain-induced increases in food availability are the most likely stimuli for these increases. The cause of population decline is not clear from this study, but predation and disease may be important factors. Radio-tracking showed that the spatial activity of the animals was concentrated on the sides of the dunes, and around burrows. Temporal activity is influenced by moonlight, with animals remaining in burrows for long periods of time on bright nights.

Rodent seed predation in cereal crop areas of central Spain: effects of physiognomy, food availability, and predation risk

Patterns of rodent seed predation in extensive cereal croplands of central Spain were investigated by measuring rodent predation rates on artificial seed patches, together with seed availability, rodent abundance and habitat physiognomy Sampling was designed to cope with the spatial and temporal variability of factors potentially affecting rodent activity (natural and man‐made habitat features, season and moonlight) Rodent predation was unpredictably distributed in summer In winter, rodents foraged on average in the patches least used by man. moonlight, however, did alter this pattern, so that rodent predation was closely associated with shrubs in the bright nights and evenly distributed in the dark ones I conclude that the need of stable underground refuges and predation risk in the winter period seemed to be the mam factors constraining rodent foraging activity in the man‐made ecosystem studied

Effects of Plant Litter on Foraging and Nesting Behavior of Prairie Rodents

Interspecific differences in seed use and location of nest sites of Peromyscus leucopus, P. maniculatus, Reithrodontomys megalotis , and Microtus ochrogaster were found among experimental patches of habitat that differed only in amount of plant litter. P. leucopus and P. maniculatus foraged selectively in patches with sparse litter and used nest boxes in these patches more than expected. R. megalotis and M. ochrogaster foraged selectively and nested in patches with moderate litter; both nested more in litter than in nest boxes. All species consumed more seeds in patches with moderate litter on bright than dark nights. P. leucopus consumed fewer seeds and P. maniculatus tended to reduce consumption from dark to bright nights; however, R. megalotis and M. ochrogaster consumed similar amounts of seeds under both light conditions. P. leucopus and P. maniculatus forage in open habitats and may perceive changes in light intensity more readily than either R. megalotis or M. ochrogaster that forage in structurally complex habitats. Interspecific differences in activity between dark and bright nights may be related to the ability of each species to detect changes in risk of predation related to variation in light intensity.

Differential Use of Experimental Habitat Patches by Foraging Peromyscus maniculatus on Dark and Bright Nights

Differential Use of Experimental Habitat Patches by Foraging Peromyscus maniculatus on Dark and Bright Nights

Relation between bright nights and meteoritic showers

From examination of published data, we find a strong correlation between the "bright-night" phenomenon and meteoritic showers. We show how the N atoms and nitric oxide molecules produced along meteor trails give a continuous emission due to NO2, the enhancement of which is at the origin of bright nights. At the same time the hydroxyl emission is enhanced.

Aspectos da ecologia dos flebótomos do Parque Nacional da Serra dos Orgãos, Rio de Janeiro: II. Distribuição vertical (Diptera, Psychodidae, Phlebotominae)

Durante um ano completo efetuamos capturas de flebótomos em isca humana, simultaneamente no solo e na copa da floresta em plataforma a dez metros de altura. Lutzomyia fischeri foi a espécie mais numerosa na copa. L.sp. 1 (espécie ainda não descrita) também foi mais freqüente neste nivel; L.shannoni, apesar de ser mais ativa ao nivel do solo, compareceu várias vezes na copa; L.pessoai, L.ayrozai, L.davisi. L.sp.2 (espécie também não identificada), L.microps e L.monticola só picaram iscas situadas no solo; L.hirsuta esteve pouco representada na copa, porém sua maior densidade foi no solo, onde figura como espécie dominante nos meses mais frios e secos do ano. Dois aspectos devem ser enfatizados com relação à distribuição vertical: a acrodendrofilia de L. fischeri e, ao contrário, o fato de L.ayrozai alimentar-se exclusivamente ao nível do solo. Este comportamento de L.ayrozai e sua preferência em sugar nas partes mais baixas do corpo fazem supor que seus abrigos naturais sejam as folhas caídas no solo florestal. Dentre os fatores mesológicos que influenciam na estratificação dos flebótomos consideramos que a luminosidade seja preponderante, pois em noites mais claras (lua crescente ou cheia) a atividade foi nula, todos os flebotomíneos capturados na copa das árvores foram obtidos em noites mais escuras (lua nova ou minguante).

Nocturnal Behavior of Four Lepidopteran Pests That Attack Tobacco and Other Crops1,2

The nocturnal behavior of the tobacco budworm, Heliothis virescens (F.), cabbage looper, Trichoplusia ni (Hubner), tobacco hornworm, Manduca sexta (L.), and soybean looper, Pseudoplusia includens Walker, was observed in a 0.4-ha cage planted to cigar-wrapper tobacco for ca. 3 months. Ambient air and dew point temperatures, night brightness, wind speed, and relative humidity were recorded in an attempt to relate these meteorological parameters to moth behavior. The general pattern of moth activity indicates early evening and early morning peaks of feeding interspersed with oviposition. Mating generally followed a period of moth flight inactivity that occurred just after the early evening peaks in feeding and ovipositional activity. Females were observed “calling” for mates during the inactive flight period, and precopulatory behavior was observed and described. The cabbage looper and tobacco hornworm generally mated earlier in the evening than the soybean looper and tobacco budworm whose mating periods were quite similar and occurred primarily between 10 PM and 4 AM. Mating occurred on both dark and bright nights, but most mating took place during dark periods. However, the tobacco plants and cage cover created an abnormally dark condition within the cage during most of the experimental period. Also, most mating occurred at temperatures near 21.1 °C and a relative humidity above 90%, but these parameters were quite uniformly high throughout the experimental period. Similarly, the wind velocities experienced in the test did not appear to influence mating behavior.

Factors affecting the distribution of rock-lobster larvae (Panulirus longipes cygnus), with reference to variability of plankton-net catches

One of the major problems in the quantitative study of the distribution of larvae of the western rock lobster Panulirus longipes cygnusGeorge, is the high variability in planktonnet catches taken at night, even when replicate hauls are made at a single station. Some of the possible causes of this variability are considered. The density of early and late-stage phyllosoma larvae caught at the surface at night showed no direct relationship to either temperature or salinity. Early-stage phyllosoma larvae were equally well represented at the surface under all light conditions encountered at night. In contrast, the density of late-stage phyllosoma larvae at the surface was, on an average, four times greater on dark nights than on bright moonlight nights. The mean density for all phyllosoma stages decreased rapidly with depth, i.e., from 0.70/1000 m3 at the surface to 0.04/1000 m3 at 25 to 35 m, indicating that the vertical movements at night are not very extensive. The density of early-stage phyllosoma larvae in the surface at night showed no relationship to micronekton biomass (measured as wet weight). Density of late-stage phyllosoma larvae at the surface at night increased slightly, but significantly, with increase of micronekton biomass, possibly indicating similar behavioural responses to light or some other factor(s). The distribution of cast exuviae of final-stage phyllosoma larvae indicated that metamorphosis to the puerulus phase can occur more than 100 miles (161 km) from shore. Moreover, 80% of the puerulus larvae caught were within 80 miles (129 km) of the shore. Mean densities of puerulus larvae taken at and below the surface at night were 0.04/1000 m3 and 0.10/1000 m3, respectively, although total numbers were low. This evidence indicates that, after metamorphosis, the puerulus larvae return to the coastal environment at some subsurface depth.

The ecology of the web ofUloborus diversus (Araneae: Uloboridae).

The distribution ofUloborus diversus webs around pack rat nests on the desert near Cave Creek, Arizona, differences between webs there and in nearby residential Phoenix, and differences between the webs of large and small individuals indicate that these spiders select web sites and designs to minimize web damage by wind. The frequency of web construction decreased when spiders in captivity were exposed to wind or to relatively bright (5 Lamberts) nights. Observations of web sites on the desert revealed high rates of web-turnover and substantial frequencies of movements of spiders from one site to another. Much lower rates of web-turnover and spider movement occurred in less windy situations in the laboratory, and in suburban Phoenix. Partial web replacement and the extension of web construction over two nights are apparently methods used to improve catching ability of sheltered (longer lived) webs by extending their surface and/or tightening their mesh.

Título en español.

1. Durante cuatro noches consecutivas completas se observaron las actividades de vuelo de la mariposa nocturna, adulto del barrenador de la caña de azúcar, para las cuales se usaron trampas que alojaban mariposas hembras como señuelo y trampas con luz negra, en los campos de caña infestados por este insecto. 2. Los adultos machos se atraparon desde las 8 p.m. hasta las 4 a.m., registrándose dos apogeos de vuelo, uno temprano y otro tardío. Así, la población de estos adultos en Puerto Rico difiere en sus hábitos de vuelo de los de la misma especie en Louisiana. 3. Las trampas de luz negra atraparon adultos hembras del barrenador de la caña de azúcar sólo durante las noches obscuras con poca o ninguna luz lunar, mientras que los adultos machos pudieron atraparse en mayor número y en las mismas trampas en las noches luminosas. Las trampas con adultos hembras como señuelo fueron igualmente efectivas tanto en las noches obscuras como en las claras. 4. La hora en que se capturaron los adultos en las trampas de luz varió de la hora en que se capturaron los adultos machos, registrándose sólo un apogeo de vuelo temprano en la noche. 5. La experiencia actual en cuanto al método de construir y preparar señuelos en las trampas de lata y en las de luz y de localizarlas en el campo indica que es necesario mejorar este método antes de que pueda hacerse un estudio más eficiente y confiable de la población de adultos del barrenador de la caña de azúcar en Puerto Rico.

The Growth of Cereals

PERHAPS nowhere is the influence of the different climatic factors on the rapidity of growth so well illustrated as on the plains of Russia. Therefore W. Kowaleuski's careful researches into this subject, summarised in the Memoirs of the St. Petersburgh Society of Naturalists (xv. 1), are especially worthy of attention. The author has gathered all necessary information for showing the periods of growth of various cereals on the soil of Russia, from the far north of Arkhangelsk, to the southern province of Kherson, and he has arrived at most interesting results, of which the following is a summary. If the periods of growth of the same cereal be taken throughout Russia, it appears that, altogether, it is in the higher latitudes that it ripens fastest. Oats and spring wheat take 123 days and barley no days to ripen about Kherson, and only 98, 88, and 98 days at Arkhangelsk, the difference in favour of the north being respectively thus: 25, 35, and 12 days. The intermediate regions show also intermediate differences, while for each latitude the growth of cereals proceeds faster in the eastern parts of Russia than in the western. It is obvious that if the rapidity of growth were due to temperature, the phenomena would be the reverse of what they are. Moreover, the want of moisture in the southern steppes is also a condition in favour of the rapidity of growth: so that it is in the insolation that we must seek for the cause of the above-stated difference. In fact, oats being usually sown about May 17 at Arkhangelsk, and the harvest usually occurring about Sept. I, the insolation continues there for 2000 hours in 98 days, not to speak of the 240 hours of bright nights; while at Kherson, during 123 days (from April 1 to Aug. 1) the insolation lasts only for 1850 hours. The difference in favour of Arkhangelsk is thus equal to 150 hours (to 400 hours, if the bright nights be added), and it compensates for the influence of temperature. It is useless to add, moreover, that the cereals cultivated in the north have already undergone a certain accommodation to their conditions. As to the intensity of light, Prof. Famintzin's work on the subject, corroborated by ulterior researches, shows that the great intensity of light in Southern Russia, combined with the great transparency of the atmosphere, is rather a condition against the rapidity of growth, the intensity of light exceeding the limits of the maximum of decomposition of carbonic acid. Winter rye shows the same differences as the spring cereals. It appears from M. Kowalewski's tables that in the Arkhangelsk district winter rye takes 375 days to arrive at ripeness, of which there are 202 days of winter rest, 68 days of autumn growth, and 105 days of spring and summer growth, making thus a total of 173 days of growth. At Kherson the total growth lasts for 290 days, of which only 101 days of winter rest and 189 days of productive growth (63 during the autumn and 126 during the summer). The difference reaches thus 16 days in favour of the north, and it would rise to 20 or 25 days if only spring and summer be taken into account. The graphical representation of all these data is most interesting. Thus the lines of simultaneous sowing of winter rye from north-west to south-east correspond to the isochirnenes, while the lines of simultaneous ripening of the spring cereals—oats, barley, sarrazin, wheat—run from south-west to north-east, corresponding to the lines of equal summer temperatures. The retarding influence of rain comes out also pretty well.