Male spiders caring for youngsters


This video says about itself:

5 December 2016

Rafael Rios Moura says spider moms handle most of the parental care, but not the Manogea porracea species he studied. Both spider parents take responsibility to protect their egg sac. Linda Rayor of Cornell University said, “To the best of my knowledge, there really aren’t other examples where male spiders step up to care for young or eggs.” Sometimes at the cost of their own lives, male Manogea porracea switch from solitary life to a dad-web upstairs, brushing rainwater off egg sacs. Moura hypothesizes that the females are very delicious to predators considering that many females disappeared by the end of breeding season.

From Science News:

First spider superdads discovered
Males give up solitary life to protect egg sacs, spiderlings — often as single parent

By Susan Milius

9:00am, December 5, 2016

The first normally solitary spider to win Dad of the Year sets up housekeeping in a web above his offspring and often ends up as their sole defender and single parent.

Moms handle most parental care known in spiders, says Rafael Rios Moura at the Federal University of Uberlândia in Brazil. But either or both parents care for egg sacs and spiderlings in the small Manogea porracea species he and colleagues studied in a eucalyptus plantation. The dad builds a dome-shaped web above the mom’s web, and either parent will fight hungry invaders looking for baby-spider lunch. In webs with no parents, only about four spiderlings survived per egg sac. But with dad, mom or both on duty, survival more than doubled, the researchers report in the January 2017 Animal Behaviour.

“To the best of my knowledge, there really aren’t other examples where male spiders step up to care for young or eggs,” says Linda Rayor of Cornell University, who has studied spider maternal care. In a group-living Stegodyphus species, some of the males in a communal web will attack intruders, but Manogea dads do much more. They switch from solitary life to a dad-web upstairs, brush rainwater off egg sacs and share defense, sometimes at the cost of their own lives.

Many male web-building spiders stop feeding as adults because they’re out searching for mates instead of catching food with their web, Moura says. Manogea males, however, stick with a female they mated with and build a new food-catching web. Now Moura would like to know whether such commitment makes males unusually choosy about females, he says.

To predators, females “must be very delicious,” Moura says. In the wild he found that many females disappeared, probably eaten, by the end of the breeding season, leaving dads as the sole protector for 68 percent of the egg sacs.

That high female mortality could have been important for evolution of the dads’ care-taking, says behavioral ecologist Eric Yip of Penn State. Just why this species has such high female mortality puzzles him, though.  Females, geared up for egg-laying, have rich nutrient stores. Yet, he says, “that’s generally true for all spiders — that females are going to be more nutritious and males are going to be mostly legs.”

Stone age monkeys and humans


This video says about itself:

13 October 2016

Clip of capuchin stone on stone percussion and licking of passive hammer associated with capuchin grooming.

Credit: M. Haslam and the Primate Archaeology Group (University of Oxford)

From Science News:

Wild monkeys throw curve at stone-tool making‘s origins

Unlike early hominids, capuchins don’t use sharp-edged rocks to dig or cut

By Bruce Bower

1:00pm, October 19, 2016

A group of South American monkeys has rocked archaeologists’ assumptions about the origins of stone-tool making.

Wild bearded capuchin monkeys in Brazil use handheld stones to whack rocks poking out of cliffs and outcrops. The animals unintentionally break off sharp-edged stones that resemble stone tools made by ancient members of the human evolutionary family, say archaeologist Tomos Proffitt of the University of Oxford and his colleagues. It’s the first observation of this hominid-like rock-fracturing ability in a nonhuman primate.

The new finding indicates that early hominids needed no special mental ability, no fully opposable thumbs and not even any idea of what they were doing to get started as toolmakers, the researchers report October 19 in Nature. All it may have taken was a penchant for skillfully pounding rocks, as displayed by capuchins when cracking open nuts (SN Online: 4/30/15).

Archaeologists have traditionally thought that ancient stone tools appeared as hominid brains enlarged and hand grips became more humanlike.

“Without the intention of making a stone tool, and with the right rock types, capuchins produce objects that are shaped like stone tools,” says University of Oxford primatologist and archaeologist Susana Carvalho, who did not participate in the new study. She suspects the earliest known stone tools were made either by relatively small-brained hominids or, perhaps in some cases, nonhuman primates. “This is not a wild idea anymore.”

The oldest known hominid stone artifacts — a set of pounding rocks and sharp-edged stone flakes — date to 3.3 million years ago in East Africa (SN: 6/13/15, p. 6). Those tools display more elaborate modifications than observed on sharp-edged capuchin creations, Proffitt says. But researchers suspect simpler hominid tools go back 4 million years or more.  Those implements might have looked more like what the South American monkeys make, he speculates.

Three capuchins tracked during an episode of rock pounding did not use fractured pieces of sharp stone to cut, scrape or dig up anything. Observations of nearly 100 rounds of rock pounding show that the monkeys sometimes recycled stone flakes as rock-pounding tools. They also often licked or sniffed powdered stone produced as they pounded rocks. Perhaps capuchins want to ingest the trace nutrient silicon, which assists in bone growth, or find lichens for some medicinal purpose, Proffitt suggests.

His team studied 60 stone fragments left behind by capuchins after rock-pounding episodes and another 51 capuchin-modified stones found in two excavations where rock pounding occurred. These artifacts included complete and broken pounding stones, stone flakes and stones that had been struck by rock-wielding monkeys.

Capuchin stone flakes are smaller and contain fewer fractured areas than ancient hominid tools, such as the 3.3-million-year-old East African finds, says archaeologist David Braun of George Washington University in Washington, D.C. But sharp-edged stones produced by the monkeys display “remarkable similarity” to artifacts from a nearby Brazilian site that some researchers think were made by humans more than 20,000 years ago (SN: 10/18/14, p. 14), Braun says. Researchers now must determine whether stone artifacts found at several South American sites dating to more than 14,000 years ago were made by humans or monkeys, he suggests.

Capuchin rock smashers’ inadvertently sharpened debris also raises questions about how hominids started making tools in the first place. Techniques for using one stone to pound away pieces of another stone, creating a rock with smooth faces bordered by razor-sharp edges, “could have been invented independently in different hominid species through [stone-pounding] behaviors we have yet to identify,” Proffitt says.

Those initial tools may have resembled capuchins’ accidentally sharpened stones or even rocks used by chimpanzees to crack nuts, says archaeologist Sonia Harmand of Stony Brook University in New York. But only hominids, and especially humans, went on to make more sophisticated stone tools and, later, everything from smart phones to space stations, says Harmand, who led the team that discovered the 3.3-million-year-old hominid tools.