Sexual selection determines parental care patterns in cichlid fishes

Despite a massive research effort, our understanding of why, in most vertebrates, males compete for mates and females care for offspring remains incomplete. Two alternative hypotheses have been proposed to explain the direction of causality between parental care and sexual selection. Traditionally, sexual selection has been explained as a consequence of relative parental investment, where the sex investing less will compete for the sex investing more. However, a more recent model suggests that parental care patterns result from sexual selection acting on one sex favoring mating competition and lower parental investment. Using species-level comparative analyses on Tanganyikan cichlid fishes we tested these alternative hypotheses employing a proxy of sexual selection based on mating system, sexual dichromatism, and dimorphism data. First, while controlling for female reproductive investment, we found that species with intense sexual selection were associated with female-only care whereas species with moderate sexual selection were associated with biparental care. Second, using contingency analyses, we found that, contrary to the traditional view, evolutionary changes in parental care type are dependent on the intensity of sexual selection. Hence, our results support the hypothesis that sexual selection determines parental care patterns in Tanganyikan cichlid fishes.     

Mitochondrial phylogeny of the endemic mouthbrooding lineages of cichlid fishes from Lake Tanganyika in eastern Africa

Of the three cichlid species flocks in eastern Africa, Lake Tanganyika harbors the oldest species assemblage, which is also the most diverse morphologically and behaviorally. For 12 species (20 individuals) of 12 genera of the tribe Ectodini, 852 bp from two segments (cytochrome b and control region) of the mitochondrial genome were sequenced. In addition, orthologous sequences were obtained from eight species (11 individuals) representing other mouthbrooding lineages from Lake Tanganyika. Comparisons of sequence divergences revealed that the single Tanganyikan tribe Ectodini appears to be approximately five times older than the whole Lake Malawi cichlid species flock, suggesting that the radiation of the Tanganyikan mouthbrooding lineages took place long before the species flocks of Lakes Malawi and Victoria evolved. Seven of nine surveyed tribes of Tanganyikan cichlids appear to be approximately equally divergent, and this seems to corroborate the hypothesis of a rapid simultaneous formation of lineages at an early stage in the history of the Lake Tanganyika species flock. The close genetic relationship between the endemic Tropheus lineage and a nonendemic "Haplochromine," Astatotilapia burtoni, indicates that members of the tribe Tropheini may be the sister group of the cichlid flocks of Lakes Malawi and Victoria. The phylogenetic analyses demonstrate the monophyly of the Ectodini and identify the Cyprichromini as their sister group among the Tanganyikan cichlids. Within the tribe Ectodini the molecular data suggest both a branching pattern different than that previously proposed and a subdivision of the Ectodini into four clades, instead of the two originally described. The previously postulated model of morphological transformations believed to be responsible for the drastically different types of ecological specialization found among the Ectodini might therefore be in need of reinterpretation. Characters immediately related to foraging and nutrition seem to be particularly prone to homoplasy, even among members of a single lineage of cichlid fishes.      

Habitat use and its implications to functional morphology: niche partitioning and the evolution of locomotory morphology in Lake Tanganyikan cichlids (Perciformes: Cichlidae)

Animal locomotory morphology, i.e. morphological features involved in locomotion, is under the influence of a diverse set of ecological and behavioral factors. In teleost fish, habitat choice and foraging strategy are major determinants of locomotory morphology. In this study, we assess the influence of habitat use and foraging strategy on important locomotory traits, namely the size of the pectoral and caudal fins and the weight of the pectoral fin muscles, as applied to one of the most astonishing cases of adaptive radiation: the species flock of cichlid fishes in East African Lake Tanganyika. We also examine the course of niche partitioning along two main habitat axes, the benthic vs. limnetic and the sandy vs. rocky substrate axis. The results are then compared with available data on the cichlid adaptive radiation of neighbouring Lake Malawi. We find that pectoral fin size and muscle weight correlate with habitat use within the water column, as well as with substrate composition and foraging strategies. Niche partitioning along the benthic–limnetic axis in Lake Tanganyikan cichlids seems to follow a similar course as in Lake Malawi, while the course of habitat use with respect to substrate composition appears to differ between the cichlid assemblages of these two lakes.     

Male foraging avoidance in female feeding territories in a harem polygynous cichlid in Lake Tanganyika

We studied foraging site partitioning between the sexes in Neolamprologus tetracanthus, a shrimp-eating Tanganyikan cichlid with harem-polygyny. Females maintained small territories against heterospecific food competitors within large territories of males, foraging exclusively at the inner side of their own territories (foraging areas). Males fed as frequently as females in their own territories, but mostly outside female foraging areas, although they frequently entered female territories and repelled food competitors from the territories. Soon after removal of the resident females, however, harem males, as well as many food competitors, invaded the vacant territories and intensively devoured prey of female foraging areas. This indicates that although female foraging areas appear to contain more food than outside the areas, harem males refrained from foraging there when the resident females were present. We suggest that harem males will attempt to keep female foraging areas in good condition, whereby they may get females to reside in male territories and/or promote female gonadal maturation.     

Territorial defense against various food competitors in the Tanganyikan benthophagous cichlid <Emphasis Type="Italic">Neolamprologus tetracanthus</Emphasis>

Territorial defense of nonbreeding female Neolamprologus tetracanthus, a shrimp-eating Tanganyikan cichlid, was investigated. Females defended territories (=home ranges, ca. 1m across) against a variety of intruding fishes. Conspecific females were usually attacked outside the territories, heterospecific benthivores (shrimp eaters) and omnivores near the border of the territories, and piscivores, algae and detritus feeders, and herbivores inside the territories. Females used some parts of the sandy substrate in the territories for foraging (foraging areas). Territorial defense prevented most of the conspecific females and benthivores from intruding into the foraging areas. In omnivores, piscivores, and algae and detritus feeders, about half the intruders were repelled from the foraging areas, although herbivores were infrequently repelled in the areas. Soon after removal of the resident females, many food competitors invaded the foraging areas and eagerly devoured prey, suggesting that the territories are maintained for food resource protection from these competitors. Females are likely to discriminate intruding fishes and change their territorial defense primarily on the basis of the degree of dietary overlap, resulting in monofunctional serial territories.     

Evolutionary history of Lake Tanganyika's scale-eating cichlid fishes

Although Lake Tanganyika is not the most species-rich of the Great East African Lakes it comprises by far the greatest diversity of cichlid fishes in terms of morphology, ecology, and breeding styles. Our study focuses on the Tanganyikan cichlid tribe Perissodini, which exhibits one of the most peculiar feeding strategies found in cichlids-scale-eating. Their evolutionary history was reconstructed from 1416 bp DNA sequence of two mitochondrial genes (ND2 and partial control region) and from 612 AFLP markers. We confirm the inclusion of the zooplanktivorous genus Haplotaxodon in the tribe Perissodini, and species status of Haplotaxodon trifasciatus. Within the Perissodini, the major lineages emerged within a short period roughly 1.5-2 MYA, which makes their radiation slightly younger than that of other Tanganyikan cichlid tribes. Most scale-eaters evolved in deep-water habitat, perhaps associated with the previously documented radiations of other deep-water dwelling cichlid lineages, and colonized the shallow habitat only recently.     

Phylogeny of the Lake Tanganyika cichlid species flock and its relationship to the Central and East African haplochromine cichlid fish faunas

Lake Tanganyika, the oldest of the East African Great Lakes, harbors the ecologically, morphologically, and behaviorally most complex of all assemblages of cichlid fishes, consisting of about 200 described species. The evolutionary old age of the cichlid assemblage, its extreme degree of morphological differentiation, the lack of species with intermediate morphologies, and the rapidity of lineage formation have made evolutionary reconstruction difficult. The number and origin of seeding lineages, particularly the possible contribution of riverine haplochromine cichlids to endemic lacustrine lineages, remains unclear. Our phylogenetic analyses, based on mitochondrial DNA sequences of three gene segments of 49 species (25% of all described species, up to 2,400 bp each), yield robust phylogenies that provide new insights into the Lake Tanganyika adaptive radiation as well as into the origin of the Central- and East-African haplochromine faunas. Our data suggest that eight ancient African lineages may have seeded the Tanganyikan cichlid radiation. One of these seeding lineages, probably comprising substrate spawning Lamprologus-like species, diversified into six lineages that evolved mouthbrooding during the initial stage of the radiation. All analyzed haplochromines from surrounding rivers and lakes seem to have evolved within the radiating Tanganyikan lineages. Thus, our findings contradict the current hypothesis that ancestral riverine haplochromines colonized Lake Tanganyika to give rise to at least part of its spectacular endemic cichlid species assemblage. Instead, the early phases of the Tanganyikan radiation affected Central and East African rivers and lakes. The haplochromines may have evolved in the Tanganyikan basin before the lake became a hydrologically and ecologically closed system and then secondarily colonized surrounding rivers. Apparently, therefore, the current diversity of Central and East African haplochromines represents a relatively young and polyphyletic fauna that evolved from or in parallel to lineages now endemic to Lake Tanganyika.     

Foraging behavior of the scale-eater Plecodus straeleni (Cichlidae,Teleostei) in Lake Tanganyika,Africa

Synopsis Sixty-nine individuals of Plecodus straeleni were followed for 1 h each in the field with the aid of SCUBA, and time budgets, hunting techniques and prey selection were investigated in relation to sex and body size. The time of cruising in midwater and on the substrate amounted to 3/4 of the total time. The rest of the time was mainly spent on five hunting techniques named pursuing, waiting, mingling, aiming and stealthy approaching. Pursuing (following a flying prey at high speed) was frequently used by adults, especially males, mainly to attack the spiny eel Afromastacembelus moorii. Waiting (keeping motionless on the substrate, waiting for a known prey) was used by some adult females when they tried to steal eggs of the mouthbrooder Cyathopharynx furcifer on the bower and by adult males when they targeted an eel having hidden under a rock. Mingling (mixing in a school of prey to attack school members) was a favorite tactic of subadults to attack plankton-feeders. Aiming (directing the head to a target fish for a moment) commonly occurred when both adults and subadults attacked solitary fishes. In stealthy approaching, the scale-eater approached an unwary prey from behind or sideway. Attacks by these hunting techniques amounted to 97% of the total attacks, which were made on 38 cichlid species and 7 non-cichlid species. Hunting techniques and prey preference varied not only with sex and size but even among consexuals of similar sizes. A number of individuals successively attacked only one or a few prey species in 1 h. Food specialization among individuals was attributed to their learning of the behavior and life style of preferred prey species.     

Modelling of essential fish habitat based on remote sensing,spatial analysis and GIS

Lake Tanganyika is not the most species-rich of the Great East African Lakes, but comprises the greatest diversity of cichlid fishes in terms of morphology, ecology, and breeding styles. The lake contains a polyphyletic assemblage of cichlid lineages, which evolved from several ancient species that colonized the emerging lake some 9–12 million years ago. Based on morphological characteristics, the Tanganyikan cichlids have been classified into 12, or, more recently, 16 tribes, which are largely supported by molecular data. The radiations of East African cichlids are believed to be driven by complex interactions between extrinsic factors, such as climatic changes and geological processes, and intrinsic biological characteristics of the involved organisms. Diversification within different lineages occurred simultaneously in response to drastic habitat changes such as the establishment of lacustrine deep-water conditions 5–6 MYA and subsequent major lake-level fluctuations. This seems particularly true for the mouthbrooding lineages whereas the substrate breeders underwent a more gradual process of diversification. This review presents an account of the taxonomy and phylogeny of the Lake Tanganyika cichlid species assemblage, its relationship to the African cichlid fauna, key factors leading to the astonishing diversity and discusses recently proposed alternative age estimates for the Lake Tanganyika cichlid species assemblage.     

Underwater observations of piranhas in western Brazil

Synopsis The behaviour of three piranha species,Serrasalmus marginatus, S. spilopleura, andPygocentrus nattereri, and their prey fishes was studied underwater in the Pantanal region, Mato Grosso, Brazil. General habits, predatory tactics, feeding behaviour, and social interactions while foraging, as well as defensive tactics of prey fishes were observed.S. marginatus is solitary whereas the other two species live in shoals; their agonistic behaviour varies accordingly, the simplest being displayed by the solitary species. Predatory tactics and feeding behaviour also vary:S. spilopleura shows the most varied diet and highly opportunistic feeding strategy, which includes aggressive mimicry. The solitaryS. marginatus, besides fin and scale-eating, occasionally cleans larger individuals ofP. nattereri. Several cichlid species display defensive tactics clearly related to piranha attacks: tail protecting, watching, and confronting the predator are the most commonly observed behaviours. Piranhas seem to strongly influence use of habitat, social structure, and foraging mode of the fish communities.     

An Adaptive Difference in the Relationship between Foraging Mode and Responses to Prey Chemicals in two Congeneric Scincid Lizards

Sensory abilities must allow efficient detection of prey, but the senses used and their relative importance may vary with hunting methods. In lizards, ambush foragers locate prey visually and active foragers use a combination of vision and vomerolfaction, the chemical sense associated with the vomeronasal system. Active foragers, but not ambush foragers, discriminate between prey chemicals and other chemical stimuli sampled by tongue-flicking. In active foragers, features of the tongue that may improve chemical sampling, such as elongation and forking are more pronounced and density of vomeronasal chemoreceptors is greater, than in ambush foragers. Foraging mode is fixed in most lizard families, and correlated evolution has been demonstrated among foraging mode, discrimination of prey chemicals, and lingual-vomeronasal morphology by interfamilial comparisons. Here I present information on a rare case of an intrageneric difference in foraging mode in the genus Mabuya . Laboratory experiments on the discrimination of prey chemicals showed that the active forager M . striata sparsa exhibits prey chemical discrimination, but the ambush forager M . acutilabris does not. The active forager also has a slightly more elongated tongue with deeper notching at the tip than the ambush forager, which might be a response to a change in foraging behavior or a reflection of unrelated differences in head shape. These findings confirm predictions based on correlated evolution between the hunting method and use of the chemical sense to locate food. They further show that chemosensory behavior is adjusted to change in foraging mode more rapidly than was previously known and suggest that behavioral changes may occur more rapidly than associated modifications of chemosensory morphology.     

Benefits of Group Foraging Depend on Prey Type in a Small Marine Predator,the Little Penguin

Group foraging provides predators with advantages in over-powering prey larger than themselves or in aggregating small prey for efficient exploitation. For group-living predatory species, cooperative hunting strategies provide inclusive fitness benefits. However, for colonial-breeding predators, the benefit pay-offs of group foraging are less clear due to the potential for intra-specific competition. We used animal-borne cameras to determine the prey types, hunting strategies, and success of little penguins (Eudyptula minor), a small, colonial breeding air-breathing marine predator that has recently been shown to display extensive at-sea foraging associations with conspecifics. Regardless of prey type, little penguins had a higher probability of associating with conspecifics when hunting prey that were aggregated than when prey were solitary. In addition, success was greater when individuals hunted schooling rather than solitary prey. Surprisingly, however, success on schooling prey was similar or greater when individuals hunted on their own than when with conspecifics. These findings suggest individuals may be trading-off the energetic gains of solitary hunting for an increased probability of detecting prey within a spatially and temporally variable prey field by associating with conspecifics.     

Recent speciation between sympatric Tanganyikan cichlid colour morphs

Lake Tanganyika, Africa's oldest lake, harbours an impressive diversity of cichlid fishes. Although diversification in its radiating groups is thought to have been initially rapid, cichlids from Lake Tanganyika show little evidence for ongoing speciation. In contrast, examples of recent divergence among sympatric colour morphs are well known in haplochromine cichlids from Lakes Malawi and Victoria. Here, we report genetic evidence for recent divergence between two sympatric Tanganyikan cichlid colour morphs. These Petrochromis morphs share mitochondrial haplotypes, yet microsatellite loci reveal that their sympatric populations form distinct genetic groups. Nuclear divergence between the two morphs is equivalent to that which arises geographically within one of the morphs over short distances and is substantially smaller than that among other sympatric species in this genus. These patterns suggest that these morphs diverged only recently, yet that barriers to gene flow exist which prevent extensive admixture despite their sympatric distribution. The morphs studied here provide an unusual example of active diversification in Lake Tanganyika's generally ancient cichlid fauna and enable comparisons of speciation processes between Lake Tanganyika and other African lakes.     

Polychromatism of the scale-eaterPerissodus microlepis (Cichlidae,Teleostei) in relation to foraging behavior

Variation in foraging behavior in a population of the scale-eaterPerissodus microlepis was studied on the northwest coast of Lake Tanganyika. Differences in body coloration were found among adult and subadult individuals, which were classified into 4 color morphs designated as Beige, Dark, Grey and Stripe. These color morphs were not strictly related to either sex or size. Each morph spent much time in specific microhabitats and had a major hunting technique that differed from other morphs. Beige morph. which predominated in number, ambushed prey at open surfaces of the substrate, whereas Dark morph used the shade of rock as an ambush site. Grey morph mixed in schools of fisheds hovering in midwater to attack school members, and Stripe morph cruised in the water column and stooped mainly at bottom-fishes. Prey preference differed among the morphs corresponding to their hunting techniques but successful attack rates were similar among them. Observations of marked individuals demonstrated adherence to particular hunting techniques and, in some cases, to particular hunting sites. Intraspecific foraging specialization is discussed in relation to the function of body color and diversity of life styles of prey fishes.     

The effect of territory quality on female preference in Metriaclima zebra

The cichlid fishes of Lake Malawi are an excellent model group with which to study adaptive radiation and speciation; due to the vast number of individual species, large variation in feeding adaptations and behaviours, and relatively recent divergence are found. Males of many cichlid species will obtain and defend lek‐like territories, where they court potential mates in addition to foraging for food. Aspects of territory quality warrant investigation because of the relationship between reproductive success and territory defence success. In this study, we tested whether the presence of a small or large food resource had any effect on the preference of a gravid female for a potential mate. The results of this experiment suggest that the presence of a large food resource increases the attractiveness of a male to a potential mate. This may suggest that the presence of food alone may not be the most important factor, or there may be a threshold amount over which females are attracted. These results indicate that certain aspects of territory quality such as habitat type or proximity to a food resource may play a role in both intersexual and intrasexual selection mechanisms: perhaps even driving and possibly accelerating the speciation of certain lineages of cichlid fishes.     

Mitochondrial phylogeny of the Lamprologini, the major substrate spawning lineage of cichild fishes from Lake Tanganyika in eastern Africa

Lake Tanganyika harbors the oldest, morphologically and behaviorally most diverse flock of cichlid species. While the cichlids in Lakes Malawi and Victoria breed their eggs exclusively by buccal incubation (termed "mouthbrooding"), the Tanganyikan cichlid fauna comprise mouthbrooding and substrate-spawning lineages (fish spawn on rocks, and never orally incubate eggs or wrigglers). The substrate-spawning tribe Lamprologini appears to occupy a key position that might allow one to elucidate the origin of the Tanganyika flock, because five riverine (therefore nonendemic) species from the Zaire River system have been assigned to this tribe, in addition to the lake's endemic species, which make up almost 50% of all 171 species known from this lake (Poll 1986). From 16 species (18 individuals) of the tribe Lamprologini, a 402-bp segment of the mitochondrial cytochrome b gene was sequenced, and, from 25 lamprologine species (35 individuals), sequences from the mitochondrial control region were obtained. To place the Lamprologini into a larger phylogenetic framework, orthologous sequences were obtained from eight nonlamprologine Tanganyikan cichlid species (13 individuals). The Lamprologini are monophyletic, and a clade of six Tanganyikan lineages of mouthbrooders, representing five tribes (Poll 1986), appears to be their sister group. Comparisons of sequence divergences of the control region indicate that the Lamprologini may be older than the endemic Tanganyikan tribe Ectodini, and short basal branches might suggest a rapid formation of lineages at an early stage of the Tanganyika radiation. It is interesting that three analyzed riverine members of the tribe form a monophyletic group; however, they are not the most ancestral branch of the Lamprologini. This might indicate that they are derived from an endemic lamprologine ancestor that left Lake Tanganyika by entering the Zaire River system. These riverine species may not have seeded the Tanganyikan radiation, as currently thought, but may have recently recolonized the river after a long period of isolation, as soon as the lake was connected to the Zaire River again about 2 Mya. Neolamprologus moorii, endemic to Lake Tanganyika, appears to represent the most basal clade of the Lamprologini. Complex breeding behavior, involving the usage of gastropod shells and associated with dwarfism, is likely to have evolved in parallel in several lineages among the Lamprologini. The tribe Lamprologini may be in need of revision, since several genera appear to be polyphyletic.      

Handed foraging behavior in scale-eating cichlid fish: its potential role in shaping morphological asymmetry

Scale-eating cichlid fish, Perissodus microlepis, from Lake Tanganyika display handed (lateralized) foraging behavior, where an asymmetric 'left' mouth morph preferentially feeds on the scales of the right side of its victim fish and a 'right' morph bites the scales of the left side. This species has therefore become a textbook example of the astonishing degree of ecological specialization and negative frequency-dependent selection. We investigated the strength of handedness of foraging behavior as well as its interaction with morphological mouth laterality in P. microlepis. In wild-caught adult fish we found that mouth laterality is, as expected, a strong predictor of their preferred attack orientation. Also laboratory-reared juvenile fish exhibited a strong laterality in behavioral preference to feed on scales, even at an early age, although the initial level of mouth asymmetry appeared to be small. This suggests that pronounced mouth asymmetry is not a prerequisite for handed foraging behavior in juvenile scale-eating cichlid fish and might suggest that behavioral preference to attack a particular side of the prey plays a role in facilitating morphological asymmetry of this species.     

Does body size influence thermal biology and diet of a python (Morelia spilota imbricata)?

Current theory predicts that larger‐bodied snakes not only consume larger prey (compared with smaller individuals), but may also have a different range of prey available to them due to their thermal biology. It has been argued that smaller individuals, with lower thermal inertia (i.e. faster cooling rates at nightfall when air temperature falls and basking opportunities are limited), may be thermally restricted to foraging and hunting during the day on diurnally active prey, and have reduced capacity to hunt crepuscular and nocturnal prey species. This predictive theory was investigated by way of dietary analysis, assessment of thermal biology and thermoregulation behaviour in an ambush forager, the south‐west carpet python (Morelia spilota imbricata, Pythonidae). Eighty‐seven scats were collected from 34 individual pythons over a 3‐year radiotelemetry monitoring study. As predicted by gape size limitation, larger pythons took larger prey; however, 65% of prey items of small pythons were represented by nocturnally active, small mammals, a larger proportion than present in larger snakes. Several measures of thermal biology (absolute body temperature, thermal differential of body temperature to air temperature, maximum hourly heating and cooling rates) were not strongly affected by python body mass. Additionally, body temperature was only influenced by the behavioural choice of microhabitat selection and was not affected by python body size or position, suggesting that these behavioural choices do not allow smaller pythons to vastly increase their temporal foraging window. By coupling dietary analysis, measures of body temperature and behavioural observations of free‐ranging animals, we conclude that, contrary to theoretical predictions, a small body size does not thermally restrict the temporal window for ambush foraging in M. s. imbricata. An ontogenetic or size‐determined switch from ambush feeding to actively foraging on slower prey would account for the differences in prey taken by these animals. The concept of altered foraging behaviour warrants further investigation in this species.     

Behaviourally mediated indirect effects: interference competition increases predation mortality in foraging redshanks

1. The effect of competition for a limiting resource on the population dynamics of competitors is usually assumed to operate directly through starvation, yet may also affect survival indirectly through behaviourally mediated effects that affect risk of predation. Thus, competition can affect more than two trophic levels, and we aim here to provide an example of this. 2. We show that the foraging success of redshanks Tringa totanus (L.) foraging on active prey was highest in the front of flocks, whereas this was not the case for redshanks foraging on inactive prey. Also, when foraging on active prey, foraging success in a flock decreased as more birds passed through a patch, while overall foraging success was not lower on subsequent visits to the same patch. Thus, redshanks foraging on active prey suffered from interference competition, whereas this was not the case for redshanks foraging on inactive prey. 3. This interference competition led to differences in activity: redshanks attaining a lower foraging success had a higher walking rate. Greater activity was associated with wider flock spacing and shorter distances to cover, which has previously been shown to increase predation risk and mortality from sparrowhawks Accipiter nisus (L.). 4. We conclude that behavioural adaptations of prey species can lead to interference competition in foraging redshanks, and thus can affect their predation risk and mortality through increased activity. This study is one of the first to show how interference competition can be a mechanism for behaviourally mediated indirect effects, and provides further evidence for the suggestion that a single species occupying an intermediate trophic level may be simultaneously top-down controlled by a predator and bottom-up controlled by a behavioural response of its prey.     

Age-dependency in hunting ability among the Ache of eastern Paraguay

This paper examines changes in hunting ability across the lifespan for the Ache of eastern Paraguay. Hunting ability is decomposed into two components-finding prey and probability of kill upon encounter- and analyzed for important prey species. Results support the argument that skill acquisition is an important aspect of the human foraging niche with hunting outcome variables reaching peaks surprisingly late in life, significantly after peaks in strength. The implications of this study are important for modeling the role of the human foraging niche in the co-evolution of various outstanding human life history characteristics such as large brains, long lifespans, and extended juvenile periods.