When zookeepers discovered that flamingos need a large flock in order to breed, it led to all kinds of creative approaches to fool the birds – mirrors, plastic yard ornaments, speakers playing bird-crowd sounds (now, zoos generally just keep more birds). I think of habitat loss and fragmentation like a flock of flamingos. There’s a certain amount required for the habitat to function properly. If the size is too small or divided, it will fail.
The Atlantic Longleaf Pine Ecosystem (a.k.a. pine barrens – a deceptive name considering the high amount of biodiversity) spanned over 35 million hectares (about the size of Germany) around the year 1500; today, only ~1 million hectares of pocket forests remain. (1)
Good news though! If habitat is restored, amphibians (including those pictured above plus Mabee’s salamander), among many other species, come back too. (2)
- D.H. Van Lear et al. 2005. History and restoration of the longleaf pine-grassland
ecosystem. Forest Ecology and Management 211:150–165
- J. C. Mitchell. 2016. Restored Wetlands in Mid-Atlantic Agricultural Landscapes Enhance Species Richness of Amphibian Assemblages. Journal of Fish and Wildlife Management. 7(2) 490-498
The term “fitness” congers images of six-pack abs, yoga poses, and 90’s spandex leotards (for me, anyway). But those images can be misleading when it comes to understanding evolutionary fitness.
Good “fitness” in evolution means “a good fit.” Organisms that fit well in their environmental niche spend less energy just trying to survive; they have more energy left over for reproduction. So fitness is often measured by the number of offspring produced.
A sloth is well camouflaged with its slo-mo movement. Many predators detect prey by movement (if we stick with the 90’s imagery, remember the T.rex in Jurassic Park “can’t see us if we don’t move”). Low metabolism in sloths means very low food requirements. One study measured sloth metabolic rate at 174 kJ (kilajoules) per day. (1) Just for comparison, an average human requires 6000-7000 kJ per day.
- Nagy, KA and GG Montgomery. 1980. Field metabolic rate, water flux, and food consumption in three-toed sloths (Bradypus variegatus). Journal of Mammalogy 61(3)465-472
A ring species includes a series of populations set around a large barrier. Each population is a little different from its neighbors, but those differences add up as the distance increases. So, as the populations meet each other on the other side of the barrier, they’ve built up so many differences that they no longer breed. It’s a wonderful example of evolution (parapatric speciation, if you’re interested).
This cutie is the Ensatina salamander which surrounds the San Joaquin valley of California.
Play. It’s well-documented in many mammals and birds. Fish have also been observed leaping over sticks and batting around balls. Frogs play-wrestle and tadpoles ride bubbles. Turtles play tug-of-war (1). Some invertebrates even play. Octopuses, and possibly spiders and wasps, have shown play behaviors too (2).
Welcome to our new playful kittens, adopted from SAFE Haven.
- Burghardt, G.M. 2015. Play in fishes, frogs, and reptiles. Current Biology. 25(1) R9-10
- Zylinski, S. 2015. Fun and play in invertebrates. Current Biology. 25(1) R10-11
The nuthatch (Sitta carolinensis) has a lot of friends. It often teams up with chickadees and titmice. While larger flocks give greater protection from predators, more species diversity within the flock improves problem solving (1). Birds in diverse groups were able to get food from a new feeder faster.
- Freeberg, T.M., S.K. Eppert, K.E. Sieving, and J.R. Lucas. 2017. Diversity in mixed species groups improves success in a novel feeder test in a wild songbird community. Scientific Reports. Volume 7, Article number: 43014.
I grew up in the great apple-producing state of Michigan. If you haven’t been to an apple cider mill during October in the mitten state, you are missing out on one of the great joys of life.
Thousands of apple varieties grew in agricultural fields when nation’s founders declared independence. Today, 80% of that diversity is gone and with it, the genetic variation that can save apples from pests, weather, and disease.
Santayana said, “Those who cannot remember the past are condemned to repeat it.” The consequences of low crop diversity were felt during the Irish potato famine in the 1840s which caused the death or emigration of a quarter of Ireland’s citizens. A pathogen entered the potato fields and spread. Since the potatoes were genetically identical, a disease that affected one could infect them all.
Today, cost and transportation constraints benefit massive agricultural operations. The efficiency of monocultures, though, threatens our food and our health. To fight off disease in genetically-similar apples, we turn to pesticides. Apples are continually cited as worst offenders for chemical coatings (fyi, the American Chemical Society recommends a baking soda solution for washing). Today, about half of apples grown in the U.S. are Red Delicious (despite tasting like wood pulp).
Consider trying some local heritage apple varieties. Apple season starts in August!
P.S. An informative Smithsonian blog post about heritage varieties of apple includes a reference to an apple sleuth who lives just down the road from me!
Camel crickets (Ceuthophilus sp.) enjoy hanging out with humans. Perhaps you provide shelter to some in your garage or basement. These insects lack one major cricket trait though – chirping. Sound production should allow camel crickets to find each other in a dark cave or crawlspace. So, why no chirps?
A Chirp Mystery
One possible reason for the lack of chirps is a high risk of predation. In other species of crickets, those who call more or longer often end up as a snack. 1, 2 While I would hope camel crickets are relatively safe from bats and birds in your basement, spiders and mice are the crickets’ major predators. Both possess a solid sense of hearing.
Many crickets have parasites who also seek hosts by sound. Chirps attract female crickets, but they also draw mama parasites searching for a cozy spot to lay eggs. The developing parasitic larvae eat the cricket from the inside, exploding out of its body as they grow. Crickets in areas with these parasites quickly evolve “chirplessness.” Do camel crickets need to worry about these “Alien” chest-bursting scenes? While they do have a doozy of a parasite (an intestinal parasite that weakens the cricket enough to ensure predation), the infections are not related to sound production.
Perhaps camel crickets simply lost their physical ability to chirp. Most crickets produce sound by rubbing their wings together. Camel crickets, though, don’t have wings. In a basement, flying is probably not the most effective means of transportation.
The Scent of a Cricket
So, how do camel crickets find each other without sound? One word: pheromones.
Pheromones are used by many cricket species to indicate dominance, reproductive readiness, and location. Camel crickets release a scent that causes them to congregate. Researchers determined the pheromone is unrelated to reproduction since juveniles move toward the scent too. Nagel and Cade3 think the pheromone prevents camel crickets from drying out. We do know the antennae detect these pheromones. In a rather disturbing experiment, researchers found that camel crickets don’t aggregate when their antennae are lopped off.
- Baily, W.J. & Haythornthwaite, S. (1998). Risks of calling by the field cricket Teleogryllus oceanicus: potential predation by Australian long-eared bats. Journal of Zoology. 244(4) 505-513.
- Hedrick, A.V. (2000). Crickets with extravagant mating songs compensate for predation risk with extra caution. Proceedings of the Royal Society B 267(1444) 671-675.
- Nagel, M.G. & Cade, W.H. (1983). On the role of pheromones in aggregation formation in camel crickets, Ceuthophilus secretus (Orthopter: Gryllacrididae). Canadian Journal of Zoology 61(1).
Trout Lilies (Erythronium americanum) pop up from the forest floor, tiny harbingers of warm weather to come. This little lily is a spring ephemeral – a flowering plant that takes advantage of that tiny window of time between the last frozen days of winter and the heyday of spring, when the forest canopy selfishly soaks up all the sun’s rays. During those few weeks, the Trout Lily breaks through a ceiling of dead leaves, and slurps up sun and nutrients to store for the rest of the year in its underground bulb. If that’s not enough, that brief time is also used to flower, produce seeds, and make sure the next generation is safely on its way. No wonder this little plant needs a rest for the remainder of the year!
Given the time limitation, the Trout Lily can’t mess around with seed distribution. It has to be done right and done quickly. Call in the ants.
Many spring ephemerals, like the Trout Lily, produce an incentive for ants to take their seeds, move them a distance away, and plant them in a safe, nutrient-rich location. Each seed has a dollop of yumminess on its outer surface, like icing on a seed-shaped cupcake (officially the “icing” is called an elaiosome, a mixture of fats and protein). Ants carry the seeds back to their nests, feed the yumminess to their larvae, and dispose of the seeds in a waste area which just happens to be a wonderfully fertile location for young seedlings to begin their lives.
Not only do ants spread seeds to new locations and give them a fertile spot to grow, they also protect the seeds from predators like mice. Ruhren and Dudash (1) placed seeds in four scenarios on the forest floor: (a) accessible to both ants and mice, (b & c) accessible to either mice or ants, and (d) inaccessible to mice and ants. The researchers found that ants secured the seeds before the mice, saving the little plants’ lives. In locales where these superhero ants have vanished, spring ephemeral populations drop 70% (2).
Want to learn more about the superhero ants (a.k.a. winnow ants)? Visit School of Ants.
- Ruhren, S. and M. R. Dudash. 1996. Consequences of the Timing of seed release of Erythronium americanum (Liliaceae), a deciduous forest myrmecochore. American Journal of Botany 83(5):633-640.
- Rodriguez-Cabal, M., K.L. Stuble, B. Guenard, R.R. Dunn, N.J. Sanders. 2012. Disruption of ant-seed dispersal mutualisms by the invasive Asian needle and (Pachycondyla chinensis). Biol. Invasions 14:557-565.
“One of the costliest substances ever produced by man” was actually produced by sea snails (Hexaplex and Haustellum sp.). The Phoenicians (in modern-day Lebanon and Syria) harvested whelks and manufactured a reddish-purple dye called Tyrian Purple. Processing just one pound of the dye required millions of snails and cost almost $100,000 in today’s dollar. The color was prized by the Romans, who used the rare and expensive cloth to designate nobility. Romans named the land that produced the dye “Land of Purple,” or Phoenicia. (1)
As you can probably imagine, destroying millions of whelks for one pound of dye is pretty unsustainable. Over time, populations of the Mediterranean snail declined and were eventually extirpated from the region. The dye industry also collapsed. Even though other sources of purple dyes were found, they paled in comparison to Tyrian purple – literally, since Tyrian purple doesn’t fade in sunlight.
Today, many more species in the Mediterranean are facing extirpation. Almost every sea resource (like snails and other mollusks, turtles, crustaceans) in the area has plummeted to less than half its past population size. (2)
Nature can be an amazing provider, if respectfully and responsibly utilized. Populations of plants and animals produce more than could ever survive, so harvesting a certain number of individuals can actually help many species. But that “certain number” is important. Harvest too much, and the populations we rely upon decline. In harming other species, we ultimately harm our own – a lesson we could learn from the Phoenicians and the snails.
- McCord, C.P. 1969. The Lowly Whelk and the Lofty Royal Purple Dye. Archives of Environmental Health: An International Journal 18(3) 379-385.
- Lotze, H.K., M. Coll, and J.A. Dunne. 2011. Historical Changes in Marine Resources, Food-web Structure and Ecosystem Functioning in the Adriatic Sea, Mediterranean. Ecosystems. 14(2): 198-222.
Take a walk in a winter forest and you can’t help but notice beech trees. Silky smooth bark and sand-colored dry leaves stick out like Christmas lights against a dull and gloomy background. While every other leaf drifted to the forest floor months ago, beech leaves hold tight like cat hair on a sweater.
It’s called marcescence – these leaves that just won’t drop – and it’s common in oak and beech (the trees are close relatives). But why keep the leaves? Are these trees just photosynthetic versions of hoarders?
One possible reason may be to protect that bud, the thin tapered structure often described as “cigar-shaped.” Inside the scaly covering are the beginnings of the new year’s growth. Hungry deer can ruin a tree’s plans for spring. But with beech trees, deer tend to get a mouthful of dry leaves whenever aiming for a yummy bud. (1)
What about attacks from smaller enemies? Insects seem to prefer infesting trees with leaves hanging on over winter. R. Karban decided to yank all the leaves off a few dozen small oaks and compare infestation levels of a tree-noshing wasp. (2) His numbers indicate that wasps prefer leaf-hoarding trees three-to-one compared to his denuded ones.
I believe Nature is constantly sending messages of wisdom if we’ll just listen. In this case, perhaps she’s saying “every action has an upside and downside, but with diversity, there’s always hope for a better future.”
- Svendsen, Claus R. 2001. Effects of marcescent leaves on winter browsing by large herbivores in northern temperate deciduous forests. Alces 37(2): 475-482.
- Karban, R. 2007. Deciduous leaf drop reduces insect herbivory. Oecologia. 153: 81-88.