For females, choosing a mate is no superficial task. Heritable genetic factors provide significant help along the choice journey, presetting female attractiveness towards reproductively favorable traits in males. Common seemingly shallow questions such as, “Is he attractive?”, or “Does he have motivation to make money?” translate on the genetic level to Is he healthy with strong genetics that will produce strong and healthy offspring, and will he be able to successfully provide for the offspring. A recent study by Erik Postma highlights the important male trait of endurance ability, and females’ propensity to pick up on this. Prehistorically, endurance could have been a basic indicator for our ancestors of a male’s optimal ability to provide in terms of hunting and gathering food across the land. Considering this, it is no surprise that in observing female attractiveness ratings towards male Tour De France competitors, Postma’s females attribute a higher attractiveness rating to males with better endurance before knowing the competitor’s actual performance scores.

To methodically explore whether women associate attractiveness with endurance ability in males, Postma created an online survey composite of 80 portraits of male participants of the 2012 Tour De France.   816 females participated in the online survey, and they only viewed the upper body ending at the shoulders of the competitors.  To take the analyses a step further, a questionnaire was included on the presence or absence of hormonal contraceptive use in the female participant, due to evidence that birth control impedes upon natural female mate choice as the pill makes the body unreceptive to fertilization.  Male competitors competed in the Tour de France after the survey, and were recorded for their time to complete the race.

Results showed a significant pattern of higher attraction scores for males who subsequently performed better in the Tour De France race. Additionally, females using the pill showed significantly lower attraction scores toward high-performing males than females who were not using the pill.

This precious mate-quality detection tool is so precious for a reason: it is a fine-tuned production over millions of years.  Our female ancestors who possessed more attentiveness to traits that favored the reproductive success of their offspring were, quite simply, those whos’ offspring survived and made for our present existence. Evolution generally selects for efficiency in processes related to reproductive success, which explains the accurate endurance judgment that these women exhibit.  In a case like this, experimental results say not to ignore your intuition when it comes to mate choice.

Postma, E. (2014). A relationship between attractiveness and performance in professional cyclists. Biology Letters, 10(2),

Bats often fly above bodies of water from dusk to early evening to drink and forage. Foraging bats use ultrasonic pulses, sounds that are inaudible to us, that are regularly synced with wing beats and respiratory cycles to orient and locate prey. Bats emit a terminal buzz while drinking which are similar to those emitted while foraging. A terminal buzz is the last pulses of an echolocation call sequence. Echolocation is the use of calls to listen to the echo that will provide them with information about how far the object is away from them. So a terminal buzz sequence is the last pulses of sound produced before reaching an object. This study sought to discover the level to which bats produce terminal buzzes while drinking in flight.

Big Brown Bat drinking water from a pond. Picture taken by Stan Cunningham

Over 6 hours of recording bats at Birdlife Australia’s Gluepot Reserve, Waikerie, South Australia, 809 drinking passes (drinking while flying low over water) by bats were recorded. Only those which touched the water and left a visible ripple on the surface were included in the study. All 809 drinking passes were accompanied by a terminal buzz call emitted before they touched the water to drink. Out of all the buzzes, 21% were in the range of 36-50 kHz range and the remaining 79% were in the 25-35 kHz range. Figure 1 shows a pattern unique to Gould’s wattled bat Chalinolobus gouldii with search phase pulses from 28 kHz to 31 kHz. Figure 2 shows a pattern with an upward sweeping tail at 43 to 45 kHz. This pattern is likely to be produced by Vepadeslus baverstocki or Vepadeslus regulus. This difference in frequency proves that bat terminal buzz sequences are not all the same and in this case can be placed into two groups. The frequency of the terminal buzz can help determine the species present.

Figure 1: Chalinolobus gouldii terminal drinking buzz

Figure 2: Vepadeslus baverstocki or Vepadeslus regulus terminal drinking buzz

To hear the difference between these two terminal drinking buzzes click the links below.

Chanlinolobus gouldii (First in real time, then in half time)   mmc1

Vespadelus sp. (First in real time, then in half time)    mmc2

Drinking water while flying is a complex aerial maneuver.  It requires very high precision and accuracy to avoid colliding with the waters’ surface. Bats that forage for insects produce a terminal buss to provide precise information about the size, shape and location of their prey. Bats also use this terminal buzz sequence to avoid obstacles in flight and to locate landing sites. Drinking buzzes provide the bat with spatiotemporal information to locate the surface before touching it with their mouth to drink. Drinking buzzes may be used in a similar fashion as foraging buzzes. This research suggests that other studies may overestimate the number of foraging buzz calls over water bodies if they were unaware of drinking buzz calls. Drinking buzzes can be used to document rates of drinking by bats in the future. The more we know about bats, the more we can do if they ever need our help.

Sources:

Cunningham, Stan. “Photographing Bats Drinking from Elephant Head Pond in Amado AZ.”           Web blog post. Cunningham Outdoors LLC. N.p., 06 Dec. 2012. Web. 14 Feb. 2014.

Griffiths, S.R. 2013. Echolocating bats emit terminal phase buzz calls while drinking on the             wing. Behavioral Processes 98:58-60.

Male Carpetan rock lizard

With all of the crazy weather occurring around the world (unbelievable—literally—snowstorms in Atlanta?), climate change is receiving increasingly more attention from the public and scientists alike. There has been extensive research on evolutionary responses to climate change and how warming temperatures might affect species ranges.

But so far there has been very little research examining the effects of climate change on the sexual signals of animals. And while the mating behaviors of humans are probably safe from global warming, the threatened Carpetan rock lizard (Iberolacerta cyreni) living in the mountains of Central Spain may not be so lucky.

(The incredibly romantic mating strategy of rock lizards) http://www.youtube.com/watch?v=1l2zlbFKi9o

A recent study conducted by researchers from the National Museum of National History in Spain tested the hypothesis that increasing environmental temperatures would lower the efficiency of the lizards’ sexual signals. These signals are incorporated into the male’s chemical secretions, which are used to mark their territories and attract females. Previous studies have shown that females spend more time in territories marked by secretions containing higher levels of provitamin D (a compound that can be converted into vitamin D), therefore increasing the mating opportunities of the male controlling that area.

The study found that higher temperatures caused these secretions to degrade more rapidly, lowering the ability of females to detect them. Females also spent less time in areas that were experimentally maintained at higher temperatures compared to areas maintained under current environmental temperatures. Degraded signals may also provide less information to females about male body size, health, and other important factors that go into mate choice.

The inability to detect sexual signals could ultimately disrupt sexual selection in rock lizards. If signals become less informative, females might begin choosing mates at random rather than choosing the healthiest and strongest males, which could affect the evolution of the species in the future.

Although species have always had to adapt to changes in climate, human-induced climate change is occurring so rapidly that many species, including the Carpetan rock lizard, may not be able to keep up. Additional research needs to be done on how global warming will affect the biology of the species in order for conservation efforts to be as effective as possible.

Reference: Martín, J., López, P. 2013. Effects of global warming on sensory ecology of rock lizards: increased temperatures alter the efficacy of sexual chemical signals. Functional Ecology, 27: 1332–1340.

There may be another way to protect yourself against mosquitoes. A new study in the Journal of Experimental Biology used mosquitoes (Aedes aegypti) in varying environments of carbon dioxide. Mosquitoes use carbon dioxide to locate a snack (i.e., your ankle). But what happens if carbon dioxide is already in the environment? Mosquitoes presumably may then have difficulty locating their blood host.

[The mosquito detected carbon dioxide from this host in order to find its meal.]

Researchers at the Swedish University of Agricultural Sciences wanted to see just how affected these mosquitoes would be by extra carbon dioxide in their hunting environment. They used a wind tunnel in which they could control background carbon dioxide levels as well as a “stimulus concentration” which acted as a host for the mosquitoes. Take-off time and time to source contact were measured. Take-off time refers to how long the mosquitoes take to decide that a host is nearby. Time to source contact refers to how long the mosquitoes take to locate this host.

When the mosquitoes were tested in an environment filled with carbon dioxide, they took more time to take-off. Not only this, but these mosquitoes also had a more difficult time detecting the stimulus concentration (fake host), even when this concentration was increased. In terms of finding this stimulus, whenever the wind tunnel had the least amount of carbon dioxide, the mosquitoes were able to find the source quicker.

To confirm these behavioral results, the study also looked at the electrical activity in olfactory-receptor neurons (also known as: nerves that detect smells) that were specific for carbon dioxide detection. The stimulation of these nerves correlated with the mosquitoes’ apparent difficulty detecting hosts in environments with high carbon dioxide levels already present. This implies that these nerves are experiencing a masking effect. So, if you’re looking for the best mosquito repellant on the market, search for a tank of carbon dioxide to fill your surrounding environment.

The researchers actually concluded this may not be necessary, though. With rising atmospheric carbon dioxide levels in our environment, mosquitoes may have a tough time adapting to these constantly rising levels. This is big news, and it begs the question: will mosquitoes stick around in our changing climate? More research is necessary to make conclusions about mosquito adaptability in terms of rising levels of carbon dioxide, however. To find out more about this phenomenon, find this article in the most recent issue of the Journal of Experimental Biology.

Majeed, S., Hill, S. R., & Ignell, R. (2014). Impact of elevated CO2 background levels on the host-seeking behavior of Aedes aegypti. Journal of Experimental Biology, 217, 598-604.

Orchid Mantis

He loves me… He loves me not… As you peel the petals off your flowers this Valentine’s Day, it may be important to ensure that it’s not an orchid mantis. Floral mimicry is most commonly found in orchids, where approximately a third of the species depend on deception for pollination. Until now, there has not been any documented case of floral mimicry occurring outside of angiosperms.

Orchid mantises are elusive creatures and are hypothesized to use floral mimicry as a means to attract pollinators as prey. Hanlon et al. (2014) applied color modeling to compare orchid mantis and flower coloration from the perspective of a hypothetical pollinator. Then, observation of behavioral responses of wild pollinators to live orchid mantises were used to test the hypothesis that the orchid mantis is a flower mimic.

Average color coordinates of orchid mantises are in the filled triangles, while the color coordinates of 13 wild flower species are shown in open triangles.

Hanlon et al. (2014) used two separate models of trichromatic hymenopterian vision: the color hexagon and the receptor noise limited model. Their results showed that the colors of orchid mantises fall within the range of flower petal colors of numerous local flowers, and the average chromatic contrast values between orchid mantises and 13 flower species were either significantly below or not significantly different from the discrimination threshold values of honeybees.

Visitation rates of wild pollinators to field stimuli.

In field experiments, Hanlon et al. (2014) found that visitation rates per-hour differed between the flower, the mantis, and the bare stick control. Wild pollinating insects, primarily bees but occasionally butterflies and flies, inspected the live juvenile female orchid mantises significantly more frequently than the bare stick. Hanlon et al. (2014) recorded two successful prey captures as well as numerous prey capture attempts by the orchid mantises; their prey capture attempts did not deter pollinating insects from inspecting and visiting the orchid mantises.

This study by Hanlon et al. (2014) confirms the mimicry hypothesis of orchid mantises: floral mimicry, in the orchid mantis, is used to attract pollinators as prey. While many species use floral camouflage to catch prey, the orchid mantis uses a more aggressive form of mimicry; pollinators are deceived and attracted to the orchid mantis rather than flowers within the general vicinity.  The orchid mantis provides some of the first evidence for floral mimicry as a predatory strategy.

For more information, here’s a neat BBC Earth video on the orchid mantis: https://www.youtube.com/watch?v=FUKyETJZqM8

Hanlon, J., Holwell, G., Herberstein, M. (2014). Pollinator deception in the orchid mantis. The American Naturalist 183:1, 126-132