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Annual estimates of population size are important for tracking long-term population trajectories. There is concern that monarch butterflies (Danaus plexippus L.) in eastern North America are declining because the Mexican overwintering colonies have been shrinking over the past 20yr. We examined a I9-yr data set of fall monarch censuses at a site in northern Michigan (Peninsula Point) to determine if the number of monarchs counted here has changed over time. At this site, volunteers walk a standardized transect daily during the fell to record migratory monarchs. Our secondary goal was to evaluate the relationship between the annual numbers at Peninsula Point and the size of the subsequent overwintering colonies. A statistical model that included multiple predictors of 1,793 census counts revealed a small but significant positive effect of year on counts, but the mean annual count number was not significantly correlated with year. In either case, we found no evidence for declines in monarch abundance. We also found no relationship between annual estimates of abundance at Peninsula Point and annual estimates of overwintering colony size. We interpret the disparity between long-term patterns here versus those in Mexico to be the result of mortality during migration or other factors that reduce migration success. Given this conclusion, we argue that preserving migratory habitats and resources, as well as reducing anthropogenic activities that hinder migration, should be the highest priorities for conserving monarchs in eastern North America. [ABSTRACT FROM AUTHOR]

Declines in overwintering colonies of monarch butterflies (Danaus plexxipus) in Mexico raise questions about other life cycle phases, such as spring migration, where monarchs recolonize their breeding range in the United States and Canada with sequential generations. We used data from a longterm citizen science program, "Journey North" (now with 18 yr), to identify possible changes to the recolonization. This program asks people to report the date and location when they see the first adult monarch annually, and this database now contains >11,000 records. We examined sighting dates and migration range size, the latter based on the number of 2-degree latitude-longitude grid squares with monarch sightings, to look for evidence of change in either of these two parameters over the 18yr. Our analyses used regression models that accounted for increasing volunteer participation over the years. We found monarchs are being sighted later at a rate of 1 d later every 4 yr. This does not appear to be related to later emergence of milkweed, based on examination of milkweed reports. Later sightings could be interpreted as a sign of reductions in monarch abundance (it takes longer to see the first monarch of the year). We also found a potential decline in the geographic range of the initial spring migration wave (a decline of 9% over 18 yr). However we detected no change in the continental area encompassed at the end of recolonization, indicating monarchs are still successfully f illing their traditional breeding range in eastern North America. [ABSTRACT FROM AUTHOR]

In polymorphic mammalian species that display multiple color forms, those with dark, or melanic pelage would be prone to overheating, especially if they live in warm climates, because their fur absorbs solar energy at a higher rate. However, experimental studies indicate that certain physical properties of fur of dark individuals appear to prevent, or minimize heat stress, although it is not clear what properties do so. Here, we tested the possibility that black-furred individuals simply have shorter or thinner hair fibers, which would create a lighter (in terms of weight) coat or one that allows greater air flow for evaporative cooling. We examined museum specimens of eastern fox squirrels Sciurus niger, a species native to the United States and one that displays brown, grey or all-black pelage color, and used image analysis procedures to quantify hairs from the dorsal surface and tail. From examination of 43 specimens (19 brown, 9 black and 15 grey), and 1,720 hairs, we found no significant difference in hair lengths across color morphs, but significant differences in hair fiber widths. Black squirrels had thinner body hairs than other forms (7% thinner), but thicker tail hairs (9% thicker) than the others. Given that the dorsal surface would be directly exposed to solar radiation, we interpret this to be an adaptation to prevent heat stress during the day. The thicker tail hairs may be an adaptation for nighttime thermoregulation, since squirrels sleep with their tails wrapped around their bodies. These results add to a growing literature body of the functional significance of mammalian pelage. [ABSTRACT FROM AUTHOR]

Mammalian pelage color can vary among individuals of many species, although this intraspecific variation is often overlooked by researchers, perhaps because of its sometimes subtle nature and difficulty in assessing it quantitatively. Thus, such variation is rarely studied in mammals, and this is especially true within the order Chiroptera, where there has been very little empirical research. We examined museum specimens of red bats (Lasiurus borealis, family Vespertilionidae) from Georgia, USA, to determine the extent of sexual dimorphism in pelage color and to explore possible associations between body size and pelage color. We photographed 54 specimens under uniform lighting, and used an image analysis program to measure pelage hue on the uropatagium region, which is fully furred in members of the genus Lasiurus. Statistical analyses of pelage hue scores showed males had significantly redder pelage than females when considered alone, but when examined together with effects of body size and collection year, sex was not significant, and collection year and body size were. More recent specimens tended to be less red than older specimens, which might indicate a wearing of the buffy tips of hairs from older specimens, and smaller bats of both sexes tended to be more red. These interesting findings are encouraging and we suggest that future explorations into intraspecific variation in pelage color of bats using this or similar approaches are warranted to clarify the significance of the patterns. This study also demonstrated that care must be taken in analyses of mammalian pelage color from older museum skins, or at least that researchers must take into account the age of the specimens [Current Zoology 56 (4): 401-405, 2010]. [ABSTRACT FROM AUTHOR]

The demands of long-distance flight represent an important evolutionary force operating on the traits of migratory species. Monarchs are widespread butterflies known for their annual migrations in North America. We examined divergence in wing morphology among migratory monarchs from eastern and western N. America, and nonmigratory monarchs in S. Florida, Puerto Rico, Costa Rica, and Hawaii. For the three N. American populations, we also examined monarchs reared in four common environment experiments. We used image analysis to measure multiple traits including forewing area and aspect ratio; for laboratory-reared monarchs we also quantified body area and wing loading. Results showed wild monarchs from all nonmigratory populations were smaller than those from migratory populations. Wild and captive-reared eastern monarchs had the largest and most elongated forewings, whereas monarchs from Puerto Rico and Costa Rica had the smallest and roundest forewings. Eastern monarchs also had the largest bodies and high measures of wing loading, whereas western and S. Florida monarchs had less elongated forewings and smaller bodies. Among captive-reared butterflies, family-level effects provided evidence that genetic factors contributed to variation in wing traits. Collectively, these results support evolutionary responses to long-distance flight in monarchs, with implications for the conservation of phenotypically distinct wild populations. [ABSTRACT FROM AUTHOR]

Throughout the animal kingdom there are species that have two or more phenotypic forms or 'morphs', and many of these are amphibians. In North America, the red-backed salamander Plethodon cinereus can have either a red dorsal stripe or no dorsal stripe (lead-phase form), and evidence to date indicates the lead-phase form incurs a greater number of attacks from predators. In a recent collection of 51 P. cinereus, blood smears of both color morphs (35 red-stripe, 16 lead-phase) were examined to obtain numbers of circulating leukocytes (via light microscopy), which can be used to indirectly estimate levels of stress hormones in vertebrates via a 'hematological stress index', which is the ratio between the number of two leukocyte types (neutrophils and lymphocytes). Our results showed that lead-phase salamanders tended to have greater numbers of circulating neutrophils and lower numbers of circulating lymphocytes than red-stripe morphs, leading to higher average neutrophil-lymphocyte ratios in lead-phase individuals. Since the salamanders were held (refrigerated) for 7 days before sampling, we cannot be certain if this effect is a stress reaction to the captivity or the normal level for this morph. However comparison with two sets of related salamanders that were captured and sampled immediately indicates the red-stripe salamanders were either not stressed from the captivity at all, or their white blood cell distributions had returned to normal after 7 days of captivity. Taken together, our results indicate that lead-phase forms of P. cinereus have higher stress levels than the red-stripe forms, which may be a consequence of their higher exposure to, and/or attacks from, predators. They may also indicate that the lead-phase form is less-suited to captivity than the red-stripe form of this species [Current Zoology 56 (2): 238-243, 2010]. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including monarch butterflies, migrating animals and value of monarchs.

Predictors of male monarch butterfly mating success have eluded researchers for years. Although it has long been known that there is variation in male mating success in this species, the source of this variation remains unclear. We used digital image analysis techniques to measure fine-scale variation in three components of the orange color (hue, saturation and brightness of the orange) of the forewings of 174 males at a level of detail that has not been possible until recently, and we compared this information to the mating success of the males in captivity. A second experiment involved addition of orange coloration to the wings of 93 males before mating trials. Our results indicate that one component of the orange color (saturation) correlated with mating success in our first experiment. Furthermore, wing color manipulations had no effect, but the original saturation values of the males in the second experiment were directly related to mating success. Our results provide the first evidence that wing color in monarch butterflies relates to mating success, and they serve as an important starting point for future research. [ABSTRACT FROM AUTHOR]

Each year in eastern North America, monarch butterflies, Danaus plexippus (L.) (Lepidoptera: Nymphalidae), undergo an annual migration to wintering sites in central Mexico. We used monarch migration census data from Cape May, NJ, over a 13-yr period (1992-2004) to test for annual and within-season variation in the numbers of monarchs seen during daily censuses and to examine the timing and patterns of migration waves. Across all years, the total number of monarchs counted over the 60-d season ranged from 452 to 15,751 with a 13-yr average of 3,490 monarchs [yr.sup.-1]. There was significant annual, diurnal, and within-season temporal variation in the census counts. Within seasons, monarch numbers increased during September up until early October, and gradually declined thereafter. Comparison of season averages across years, which we consider indices of population size in the northeastern United States, indicated a highly fluctuating population size with the lowest year on record in 2004. We also found that greater than average daily counts, which we termed "notable migration days," were reported for an average of 19 d per season. On average, seven "migration waves" occurred each year, defined as a period of one or more notable migration days separated by below average days. Waves lasted an average of 3 d and were separated from others by ≈6 d. There was no significant interannual variation in wave duration or time between waves. Our 13-yr study is the longest standardized census of the monarch's fall migration, and we believe its continued operation can provide insights into the population trends of monarchs in the northeastern United States, which may reflect long-term trends from other populations in North America. [ABSTRACT FROM AUTHOR]

Since 1996, the numbers of migrating monarch butterflies stopping over at Peninsula Point, Michigan, have been monitored by volunteers during the fall migration with standardized daily counts. In this study, we describe this project and examine: 1) general patterns of migration and stopover of monarchs at this site, and 2) how environmental conditions influence monarch stopover frequency. We tested for yearly, seasonal, and diurnal variation in monarch counts within each season. We further combined these data with basic weather information recorded at the time of each count to explore the effects of wind direction and speed, temperature, and cloud cover on monarch stopover abundance. A total of 22,539 monarchs was counted over 7 yr, with yearly totals ranging from 757 in 1998 to 6,638 in 1997. Over the 7-yr period, an average of 29 monarchs was recorded per count at Peninsula Point. Interestingly, in the migration season immediately following a major population decline at overwintering sites in Mexico, the total number of monarchs counted at Peninsula Point was not significantly different from long-term average counts. The timing of the peak of migration was not consistent from year to year, and there were few consistent temporal trends within seasons. More monarchs were counted with walking transects during the day than with a roost count in the early morning. Furthermore, more monarchs were counted earlier in the season than later. Of the environmental variables we examined, wind direction had a significant influence on the number of monarchs recorded on each count with higher counts during north winds. Cloud cover also influenced monarch counts, so that the number of monarchs observed increased with temperature and decreased with cloud cover. Based on the large numbers of monarchs that stop there each fall, we suggest that Peninsula Point represents an important monarch stopover site, and thus has the potential to increase our knowledge of monarch migration and stopover ecology greatly. [ABSTRACT FROM AUTHOR]