Tool Use in Fishes

Tool use was once considered the sole domain of humans. Over the last 40 years, however, it has become apparent that tool use may be widespread across the animal kingdom. Pioneering studies in primates have shaped the way we think about tool use in animals, but have also lead to a bias both in terms of our expectations about which animals should be capable of using tools and the working definition of tool use. Here I briefly examine tool use in terrestrial animals and consider the constraints of the current working definition of tool use in fishes. Fishes lack grasping limbs and operate underwater where there are clear constraints with respect to the physics of tool use that differ dramatically from the terrestrial environment. I then examine all of the documented accounts of tool use in fishes. The review reveals that tool use seems to be confined to a limited number of fish taxa, particularly the wrasse, which may show similarities with the greater than expected number of examples of tool use in primates and corvids amongst mammals and birds, respectively. As fish are seldom studied as intensely as birds and mammals, there is a clear need for further observation of tool use in fishes. It is likely that further examples will be unveiled allowing us to perform comparative analyses of the evolution of tool use in fish

Reproductive characteristics of wild female Phayre's leaf monkeys

Understanding female reproductive characteristics is important for assessing fertility, interpreting female behavior, and designing appropriate conservation and captive management plans. In primate species lacking morphological signs of receptivity, such as most colobines, determination of reproductive parameters depends on the analysis of reproductive hormones. Here, we use fecal hormone analysis to characterize cycle patterns ( N =6 females) and gestation length ( N =7 females) in a group of wild Phayre's leaf monkeys ( Trachypithecus phayrei crepusculus ) in Phu Khieo Wildlife Sanctuary, Thailand. We found that both fecal estrogen (fE) and progestin (fP) levels showed clear biological patterns indicative of ovulation and conception. However, because fP patterns were inadequate in determining the end of the luteal phase, we used fE rather than fP patterns to delineate menstrual cycle parameters. We found a mean cycle length of 28.4 days ( N =10), with follicular and luteal phases of 15.4 ( N =10) and 12.5 days ( N =14), respectively. On average, females underwent 3.57 ( N =7) cycles until conception. Average gestation length was 205.3 days ( N =7), with fE levels increasing over the course of pregnancy. Overall, the reproductive characteristics found for Phayre's leaf monkeys were consistent with results for other colobine species, suggesting that fecal hormone monitoring, particularly for fE metabolites, can provide useful reproductive information for this species. Am. J. Primatol. 72:1073–1081, 2010. © 2010 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78228/1/20866_ftp.pd

The Ecological Conditions That Favor Tool Use and Innovation in Wild Bottlenose Dolphins (Tursiops sp.)

Dolphins are well known for their exquisite echolocation abilities, which enable them to detect and discriminate prey species and even locate buried prey. While these skills are widely used during foraging, some dolphins use tools to locate and extract prey. In the only known case of tool use in free-ranging cetaceans, a subset of bottlenose dolphins (Tursiops sp.) in Shark Bay, Western Australia habitually employs marine basket sponge tools to locate and ferret prey from the seafloor. While it is clear that sponges protect dolphins' rostra while searching for prey, it is still not known why dolphins probe the substrate at all instead of merely echolocating for buried prey as documented at other sites. By ‘sponge foraging’ ourselves, we show that these dolphins target prey that both lack swimbladders and burrow in a rubble-littered substrate. Delphinid echolocation and vision are critical for hunting but less effective on such prey. Consequently, if dolphins are to access this burrowing, swimbladderless prey, they must probe the seafloor and in turn benefit from using protective sponges. We suggest that these tools have allowed sponge foraging dolphins to exploit an empty niche inaccessible to their non-tool-using counterparts. Our study identifies the underlying ecological basis of dolphin tool use and strengthens our understanding of the conditions that favor tool use and innovation in the wild

Abrasive, Silica Phytoliths and the Evolution of Thick Molar Enamel in Primates, with Implications for the Diet of Paranthropus boisei

Background: Primates—including fossil species of apes and hominins—show variation in their degree of molar enamel thickness, a trait long thought to reflect a diet of hard or tough foods. The early hominins demonstrated molar enamel thickness of moderate to extreme degrees, which suggested to most researchers that they ate hard foods obtained on or near the ground, such as nuts, seeds, tubers, and roots. We propose an alternative hypothesis—that the amount of phytoliths in foods correlates with the evolution of thick molar enamel in primates, although this effect is constrained by a species ’ degree of folivory. Methodology/Principal Findings: From a combination of dietary data and evidence for the levels of phytoliths in plant families in the literature, we calculated the percentage of plant foods rich in phytoliths in the diets of twelve extant primates with wide variation in their molar enamel thickness. Additional dietary data from the literature provided the percentage of each primate’s diet made up of plants and of leaves. A statistical analysis of these variables showed that the amount of abrasive silica phytoliths in the diets of our sample primates correlated positively with the thickness of their molar enamel, constrained by the amount of leaves in their diet (R 2 = 0.875; p,.0006). Conclusions/Significance: The need to resist abrasion from phytoliths appears to be a key selective force behind the evolution of thick molar enamel in primates. The extreme molar enamel thickness of the teeth of the East African homini

Nut-cracking behaviour in wild-born, rehabilitated bonobos (Pan paniscus): a comprehensive study of hand preference, hand grips and efficiency

There has been an enduring interest in primate tool-use and manipulative abilities, most often with the goal of providing insight into the evolution of human manual dexterity, right-hand preference, and what behaviours make humans unique. Chimpanzees (Pan troglodytes) are arguably the most well-studied tool-users amongst non-human primates, and are particularly well-known for their complex nut-cracking behaviour, which has been documented in several West African populations. However, their sister-taxon, the bonobos (Pan paniscus), rarely engage in even simple tool-use and are not known to nut-crack in the wild. Only a few studies have reported tool-use in captive bonobos, including their ability to crack nuts, but details of this complex tool-use behaviour have not been documented before. Here, we fill this gap with the first comprehensive analysis of bonobo nut-cracking in a natural environment at the Lola ya Bonobo sanctuary, Democratic Republic of the Congo. Eighteen bonobos were studied as they cracked oil palm nuts using stone hammers. Individual bonobos showed exclusive laterality for using the hammerstone and there was a significant group-level right-hand bias. The study revealed 15 hand grips for holding differently sized and weighted hammerstones, 10 of which had not been previously described in the literature. Our findings also demonstrated that bonobos select the most effective hammerstones when nut-cracking. Bonobos are efficient nut-crackers and not that different from the renowned nut-cracking chimpanzees of Bossou, Guinea, which also crack oil palm nuts using stones

The nutritional content of Tana River yellow baboon (Papio cynocephalus) foods in a partially forested habitat.

Here we report the first dietary macronutrient and mineral content information for a little-studied yellow baboon group (i.e., the Mchelelo troop) at the Tana River Primate National Reserve, Kenya. We compare forest to savanna samples for this troop found in a partially forested habitat. Observations conducted between 1988 and 1992 determined our list of foods. Subsequently, flora samples, representing 56 species, were collected between April 2008 and March 2009 with nutrient content determined via standard procedures for fiber, gross energy, ash/minerals, crude protein, and crude fat/lipids. Concentrations of specific minerals (calcium, iron, magnesium, manganese, phosphorus, potassium, zinc) were also measured. We predicted forest items would be higher in gross energy and lipids and savanna items higher in crude protein, fiber, and minerals. Our analyses support only the predicted difference in crude protein for savanna items for the overall dataset. In our examination of the top 15 foods, savanna items had significantly higher crude protein, ash, magnesium, and manganese while forest items had higher gross energy. Right-angled mixture triangles show some clustering by location but with substantial overlap in values. Our data provide further indication of the particularity and purposefulness of dietary choices made by primates. They also contribute to the broader discussions of primate nutritional ecology and are a first step towards an examination of macronutrient balancing for this group. Finally, we discuss the impact heavy reliance upon forest products by a "savanna species" may have upon competitors and forest composition. Ultimately, we show that there is still much to be learned about baboon nutrition