Wolf Spider Facts and Population Changes in the Warming Arctic
Wolf Spiders and Two Arctic Species
Wolf spiders are impressive hunters with good eyesight. The vast majority don’t create webs. Instead, they either hide and lunge for their prey as it passes by or chase the prey and grab it. The latter behaviour gave them their name. The animals are capable of moving fast. They are venomous, but the venom generally doesn't have a serious effect on humans. The spiders are widespread and found in most parts of the world.
Multiple species of wolf spiders live in the Arctic. Researchers have discovered that the increasing temperature there is having an effect on at least two of the species. One group of scientists has discovered that Pardosa glacialis is currently reproducing twice in the summer instead of once. Another group has found population and chemical changes in Pardosa lapponica. The changes suggest that cannibalism in the species has significantly increased.
Wolf Spider Classification
Spiders belong to the phylum Arthropoda and the class Arachnida. Wolf spiders belong to the family Lycosidae within the class Arachnida. The family contains over 2,000 species and perhaps over 3,000. The number varies according to the source of the data.
Physical Features of the Arachnid
Spiders have different features from insects. Both animals belong to the phylum Arthropoda, but spiders are classified in the class Arachnida instead of the class Insecta. Members of the class Arachnida are sometimes referred to as arachnids. The class also includes scorpions, ticks, mites, and other animals.
A wolf spider may be brown, tan, orange, grey, or black. Some species are mainly one colour while others bear stripes or other markings of another colour. The body is hairy and consists of two sections: the cephalothorax and the abdomen. The sections are joined by a short stalk, which is usually obscured when a spider is seen. The cephalothorax has a humped appearance, as can be seen in a side view of the spider. It resembles a roof attached to slanting walls. Spinnerets at the end of the abdomen release silk.
The animal has eight legs arranged in four pairs. It also has a pair of chelicerae, or jaws, in the front of its mouth. An appendage known as a pedipalp can be seen on each side of the chelicerae. The pedipalps are sensory structures used for smell and taste. They are also used by the male to insert sperm into a receptacle in the female's body.
The spider has eight eyes. The two largest ones are located at the front of the head. Four small ones lie underneath the large ones. The other two eyes are located on the top of the head and are widely separated. The spider's vision is described below.
The animals don't have ears, but various parts of their body have sense organs that can detect vibrations. Some of the hairs on the body of the arachnids are sensitive to vibration and touch.
Wolf Spider Vision
A wolf spider's eyes have a lens, which focuses light rays on the retina. The retina is stimulated by the light rays. Some of the eyes have a tapetum lucidum behind the retina. The tapetum reflects light that has passed through the retina back to it, giving the light-sensitive cells another chance to be stimulated. This process improves night vision. Wolf spiders are often active at night and rest during the day. The tapetum produces a glowing appearance when light strikes it, a phenomenon known as eyeshine.
Although the eyes of wolf spiders have similar parts to ours, the eyes aren't as well developed as human ones and the arachnids can't see as well as us. They are said to have good vision compared to many other spiders, however. Experiments have shown that they can see green and ultraviolet light but no other colours.
Daily Life in the Family Lycosidae
Almost all wolf spiders live in burrows and don't produce webs. It's not correct to say that none of them make webs, however. One of the references below mentions two wolf spider species in Uruguay that do build webs. The silk released from the end of a spider's abdomen is used for additional purposes. It's used to attach the female's eggs to her body, for example.
Outside of the Arctic, wolf spiders are found in leaf litter in forests, in grasslands, and by ponds and streams. Like their relatives, they are carnivores. They actively hunt for small animals, including insects, small invertebrates such as springtails, and other spiders. Sometimes they wait for their prey to come to them and then pounce on the unsuspecting animal. Wolf spiders are in turn prey for larger animals.
Spiders often hide and become dormant during winter as the temperature drops. In this condition, they can survive without food for a long time. Some find an area under snow that is warm enough for limited activity.
Some species of spiders are able to survive during a cold winter by producing chemicals that act as an antifreeze. This prevents their cells from freezing. Researchers suspect that some spiders have more adaptations for winter survival that just antifreeze chemicals, however, because these animals survive at very low temperatures.
I haven't seen any scientific reports specifically describing how Arctic wolf spiders survive the winter, but it may well be by the same method as other spiders adapted for freezing winter temperatures.
Reproduction in Wolf Spiders
Both of the Arctic wolf spiders mentioned below belong to the Pardosa genus. In the video above, a male Pardosa amentata is "dancing" to attract a female. The male raises and then vibrates his pedipalps and front legs to attract the female's attention. The female may allow him to mate after this display. A male's pedipalps are bigger than a female's.
At first, the collection of eggs looks like a large ball and is attached to the female's spinnerets, as shown in the photo above. When the youngsters hatch, they climb onto their mother's back, or the top of the cephalothorax.
Wolf spiders are not considered to be dangerous to humans. There are some important points to consider with respect to safety, however, as described below.
Wolf Spider Bites and Venom
Wolf spiders are not aggressive, but they will bite if they are threatened. They shouldn't be handled. The bite and the venom aren't considered to be a serious problem for humans, but there are exceptions. If someone is allergic to the venom, the results may be serious and the person may require medical help. In addition, a bite causing major pain shouldn't be ignored because it's believed to have come from a wolf spider. The spider that bit the person may have been misidentified and may be one that causes more serious problems than a wolf spider.
Even if a specific species of spider is not considered to be dangerous for humans, a bite area should be cleaned, bandaged, and treated like any other wound. If the wound is large or painful, if an infection or further symptoms develop, or if a person has any concerns about the wound, medical aid should be sought.
Arctic Climate Change
The Arctic is currently warming at a faster rate than the average for the rest of the Earth. The reasons for the phenomenon are beyond the scope of this article. The National Snow and Ice Data Center reference below provides an explanation for the situation.
Pardosa glacialis Reproduction in the Arctic
A group of scientists has been studying wolf spiders living around Zackenberg in Greenland. The scientists have observed that in the last two decades snowmelt in the area has occurred "progressively earlier" and temperature has increased.
The scientists investigated Pardosa glacialis, a common wolf spider in the Arctic. Researchers knew that outside of the Arctic the female of the species often produces two egg clutches per year. Now females are producing two clutches in the Arctic instead of the single one that they used to produce.
Some of the female Pardosa glacialis spiders in the Zackenberg area have been collected in pitfall traps since 1996, enabling changes over time to be recognized. The scientists have discovered the following facts.
- In years when the snow melts earlier, the females lay their first clutch earlier and the proportion of females that produce a second clutch before the season ends is larger.
- Larger females tend to produce larger first clutches.
- The size of the female doesn't affect the size of her second clutch.
Assuming the extra babies produced as the climate warms survive, the increased spider population could have an important effect on the Arctic ecosystem. Arctic spiders feed on small animals known as springtails. The springtails feed on fungus. The food chain and the environment might be affected by an increased number of spiders.
Arctic temperatures are currently rising at twice the global average and climate projections indicate that the Arctic will continue to warm at a higher rate than the rest of the globe, which will lead to longer growing seasons— Toke T. Høye et al, The Royal Society Publishing
Changes in the Pardosa lapponica Population
Other scientists have also been studying the effects of increased temperature on wolf spiders. In addition, they have investigated the fate of the young spiders born in a warming climate. The species explored in the research was different from the one in the Greenland research, however, and the research was done in Alaska, not Greenland.
The researchers investigated wild and captive spiders in the Pardosa lapponica species. They found that as the females became bigger and produced more offspring, cannibalism apparently increased. This may have been due to increased competition for food in the group. The discoveries are summarized below.
- Wolf spiders tend to become larger as the climate warms.
- Larger females produce more offspring (or at least, more eggs).
- Unexpectedly, the researchers found that when the females in a wild group were larger and more eggs were produced, fewer juveniles existed than would be expected.
- The researchers performed a chemical analysis to detect specific components in the bodies of spiders in the wild group described above and in experimental high-density groups and lower-density ones. The results suggested that when many spiders were present in a group, the animals were more likely to eat other spiders.
- Wolf spiders that ate only other wolf spiders didn't live as long as those that ate a wider variety of food.
As in the previous research, the results are interesting and suggest that certain consequences will follow based on the observations that were made. It's unknown whether these consequences will actually happen, however.
The Future of Life in the Arctic
The results of the studies described above show that a warmer climate may have several effects on Arctic wolf spiders. Understanding the population dynamics of the animals in their natural habitat as the climate changes may not be as easy as imagined. At the moment, some speculation is involved in predicting the effects of changes in the spider population. The topic is important because the animals influence other life forms in their ecosystem as well as the non-living part of the environment.
The increasing temperatures in the Arctic are worrying for multiple reasons. It's important to understand the effects of the changing conditions on the organisms that live there and on the Arctic habitat.
- Wolf spider entry from the Encyclopedia Britannica
- Information about wolf spiders from the Missouri Department of Conservation
- More information about the spiders from PennState Extension
- Wolf spider vision from the ScienceDaily news service
- Silks in web-building wolf spiders from The Science Breaker (a partner of the University of Geneva)
- Spiders in winter from the Burke Museum
- Climate change and Arctic amplification from the National Snow and Ice Data Center (NSIDC)
- Earlier springs enable Arctic wolf spiders to produce a second clutch from The Royal Society Publishing
- Wolf spiders may be turning to cannibalism in the Arctic from the phys.org news service
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
© 2020 Linda Crampton