Female traits associated with Mammal Social Evolution [Cooperation (Hamilton); Complex Sociality (specialization)] ... CB Jones, 10/2023

 

Female traits associated with Mammal Social Evolution [Clara B. Jones October 2023]

see 1st blogpost in this blog [link below], Mammal Social Evolution: Major Transitions Approach-- also, available at lulu dot com in hard copy or pinned to my Profile on Twitter [X], @cbjones1943 [see West et al. 2015, cited below]... see, also, cited book linked to my Twitter [X] profile concerning mantled howler monkey (Alouatta palliata) female life-history strategies ...

https://vertebratesocialbehavior.blogspot.com/2022/11/mammal-social-evolution-major.html

c.f. for an early, classic, treatment of Mammal Evolution, including, group-living mammals, see Eisenberg (1971); for an early treatment of females and Mammal Social Evolution, see Wittenberger (1980); among other points, Wittenberger (op. cit.) argued that, for all intents & purposes, mammal females are the "social" sex ... West et al. (2015) is a necessary introduction to "major transitions" & social evolution ...

Terminology & Context: Terminology in the field of Social Biology, here, related to Social Evolution, is not standardized ... for example, WD Hamilton & Stu A. West, define "social" in different ways, the former limiting use of "social" to Cooperation & Altrusim, the two [of four] categories of behavior [Selfish, Cooperation, Altruism, Spite] in which Recipient gains "fitness" benefits ... West, on the other hand, defines "social" as any interindividual interaction where either or both interactants benefit reproductively ... recall that "interdependence" is a necessary precursor to Cooperation, while Cooperation is a necessary precursor to the evolution of Complex Sociality ... here, I am thinking of Cooperation as per Hamilton's general formulation--an interindividual interaction in which both interactants benefit in "fitness"  ... related to the Major Transitions Approach, Complex Sociality [division-of-labor (cooperation between specialists); task, role, &/or morphological specialization] is, particularly, problematic, it seems to me ... if we view specialization along a continuum, say, from feeding specialization to DoL to reproductive DoL with "totipotent" [female] workers or "helpers" to reproductive DoL with more or less "sterile castes" [social insect workers], do we accept the typical usage whereby Advanced Eusocial taxa are the most "complex" societies [the "pinnacle" of sociality as per Wilson (1971)]? ... though many Social Scientists would claim that interindividual interactions in humans represent the "pinnacle" of Complex Sociality, expert consensus among Social Biologists (e.g., Crespi 2014) have concluded that humans cannot be classified, Eusocial, because this species does not display "reproductive division-of-labor," although, the mechanism, Learning, permits humans to maximize the benefits and minimize the costs of generalization & specialization [e.g., (learned) division-of-labor] ... it is worth pointing out that the wide variety of human reproductive structures have not been systematically described, classified, or diagnosed, including, analysis of populations in which more than one architecture is found, such as all modern nation-states [e.g., monogamy, polygamy, promiscuity, etc.] ... whether & how & why these various conformations interact over Time & Space remains to be determined ... it is assumed that 1st Principles [T, E, acquisition, consumption, allocation] relative to abiotic [e.g., climate] & biotic [e.g., food dispersion; breeding sites] environmental regimes, as well as, constraints of limiting resources, as well as, species-typical female traits, always apply ...

Most Mammals are "sexually segregated"* [sometimes termed, "solitary" in the literature], with polygynous male home ranges or territories overlapping the home ranges or territories of however many females he can monopolize ... however, aggregations [temporary clumping of animals] may occur around clumped, limiting resources, especially, food [as, white-tailed deer may do in Spring when food is abundant & clumped]; other aggregations may form when animals migrate from one feeding &/or breeding ground to another; the term "herds" often refers to an aggregation ... the term, "group," is reserved for a reproductive unit ... Hamilton's Rule [rb - c>0 ----> rb > c] is widely accepted as a general formulation of Social Evolution ... according to Hamilton (1964), "social" behavior is limited to Cooperation & Altruism--the only conformations of interindividual interactions [Selfish, Cooperation, Altruism, Spite] whereby Recipient gains in "fitness" ... this definition of "social" should be derivable from Hamilton's equations ...

Mammalian phenotypes are usually generalized (see Eisenberg op. cit.) though there are noteworthy exceptions, & many mammal species display generalized, as well as, specialized, traits ... the evolution of Complex Sociality requires Specialization [division-of-labor; task, role, &/or morphological specialization]; Interdependence [among interacting group members] is a necessary precursor to the evolution of Cooperation ... since Cooperation is a necessary precursor to the evolution of Complex Sociality, specialization must evolve at some point during the Cooperation "grade" ... Hamilton (op. cit.) classifies "cooperation" as an interaction in which both Actor & Recipient benefit reproductively ... as a significant aside, in taxonomic studies, "specialization" is used to diagnose "primitive"/"ancestral" from "derived"/recent characters, where "specialization" is a criterion for "derived" classification ...

Depending upon environmental regime, an advantage of a generalized phenotype is promotion of phenotypic flexibility [reversible response] &/or phenotypic plasticity [irreversible response]--responses that are usually condition-, context-, situation-dependent ... in extreme &/or highly time-varying environments, responses may be "decided" statistically or probabilistically, even under Hamilton's Rule [op. cit.; often termed "kin selection"] ... it is worth pointing out that a] Hamilton's Rule [rb - c >0 ----> rb>c] does not predict that it is always beneficial to assist the reproduction of kin] the evolution of sociality does not necessarily require individual recognition, e.g., "greenbeards" may operate or "decisions" may be based on probabilities or likelihoods ...

The observation that most mammalian phenotypes are more or less generalized is usually attributed to evolution in time-varying environments ... because most mammalian phenotypes are generalized & because Complex Sociality requires the evolution of specialization, it is expected that Complex Sociality, &, possibly, Cooperation, would be uncommon in the Class & in other taxa with generalized phenotypes ... except for cooperatively-breeding mammals & the [eu]social mole rats, reproductive division-of-labor [cooperation between specialists] has not been described to date in mammals, though, "temporal division-of-labor" ["age polyethism"] has been described for mantled howler monkeys (Jones op.cit.) and probably exists in numerous other species, particularly, folivore/herbivores relying on "clumped" limiting resources [e.g., food] ... "bioaccumulation" has been proposed for the evolution of TDL in mantled howler monkeys [see blogpost above] task, role, & morphological specialization are described so far only for the social [eusocial] mole rats & is learned in humans ... several other species of mammals are potential candidates for specialization [see David Macdonald's edited reviews of Mammal Orders, and many species of mammals exhibit both generalized & specialized traits ... in humans, whose phenotypes are generalized in the mammalian mode, the evolution of learning mechanisms permits [learned] specializations such as division-of-labor and task, role specialization ... learning may have evolved in mammals with generalized phenotypes, in part, to minimize the costs of solitary living and maximize the benefits of group-living ... the question of whether morphological specialization has evolved in humans has not, to my knowledge, been systematically studied in humans; however, Race [ecotype] may be a candidate for morphological specialization in Homo sapiens ...

Since most mammals' phenotypes are more or less generalized, the evolution of Complex Sociality [&, possibly, Cooperation] is expected to be severely constrained in the Class ... however, it is noteworthy that some mammals are specialists, & many mammals are characterized by both generalized & specialized traits ... importantly, some mammalian characteristics [e.g., Learning; phenotypic flexibility (reversible) & phenotypic plasticity (irreversible) may have been favored by selection to minimize the costs & maximize the benefits of Generalization &/or Specialization.

1... females are expected to be "energy-maximizers," males, "time-minimizers" (Schoener 1971), a formulation based on 1st Principles ... all female [&/or male] traits/phenotypes should be investigated & measured relative to 1st Principles [Physics: T, E; Ecology: acquisition, consumption, allocation [to survival, &, especially, reproduction] ... see Bateman for evolution of female & male life-history trajectories ["fitness optima"] from initial gamete size [eggs large & costly to produce; sperm many & cheap to produce] ... the evolution of any phenotypic trait can be partitioned into G[enetic] x E[nvironmental] components ... 1st Principles influencing individual [genotype] "fitness" may result from variability of abiotic &/or biotic factors, e.g., climate; dispersion of limiting resources, especially, food, mates, where "dispersion" is the distribution & abundance of limiting resources in Time & Space; interactions with other group members [interindividual events], etc. ... interindividual interactions may be beneficial to, deleterious to, or neutral with respect to an individual's [an entity's] lifetime reproductive success ["fitness"] ... it is imperative for Behavioral Ecologists studying mammals [& other Vertebrates] to investigate the many strategies that have evolved to reduce reproductive, especially, maternal costs ... these strategies often take the form of females' reducing maternal care by one means or another [e.g., "parking;" reduction of fat in milk; evolution of precocial young; "bet hedging;" seasonal breeding, etc.] ... human females are extreme in these strategies since they can reduce maternal costs completely, including, the metabolic costs of ovulation [by culling eggs] ...

2... Vertebrates, social behavior [Cooperation, Altruism, as per Hamilton op. cit.] & Complex Sociality [specialization*], cannot evolve unless females transition from breeding in a solitary state to breeding in a group* [a "bauplan"], & it is important to define what "breeding in a group" can mean ... for example, the offspring of solitary mammal breeders may disperse when the next generation is produced--or, soon after ... this solitary state may, depending upon relative costs & benefits to breeders, including, species-typical traits & environmental regime [abiotic & biotic], evolve to a state whereby young from one generation overlap with the next generation, a precondition for the evolution of Complex Sociality [Specialization, as per "reproductive division of labor" characterizing Cooperative Breeding & Eusociality] ... more commonly in mammals, breeders may form communal units ... other conformations exist, such as, Chimpanzees (Pan troglodytes) for which females coexist more or less in a solitary state with their young in association with other females breeding in a more or less solitary state on overlapping home ranges [also see breeders' conformations in other non-human great apes] ... in this system, related, collaborative [cooperative?] males monopolize some number of female home ranges, & the female sex disperses--opposite from the norm in Mammals ... all non-human ape breeders exhibit a more or less solitary mode of maternal care ... the chimp, and other non-human ape sociosexual pattern may have evolved to minimize costs of breeding in a solitary state while maximizing benefits of breeding in a group, e.g., predator defense, access to mates ... a similar tradeoff may explain the female reproductive strategy in mantled howler monkeys (Alouatta palliata) whereby females breed in a more or less solitary state embedded within a multimale-multifemale sociosexual group structure ... each of the aforementioned examples is characterized by female traits minimizing maternal costs ... female reproductive strategies described for all mammalian sociosexual systems can be assessed for mechanisms to reduce maternal costs [primarily, gestation &, especially, lactation], e.g., "parking" young in protected place, usually, associated with reduced number of nursing bouts; reducing amount of fat in milk--in a few mammalian species, the amount of fat varies with stage of infant development; in groups, mothers may reduce maternal costs by receiving "help" from other group members [usually, other female offspring or female kin], sometimes termed, "allomothering" (Hrdy 1976); mantled howler monkeys reduce the duration of maternal care combined with harsh weaning of young as soon as the issue can feed on its own ... the great apes, except humans, are an interesting case because females breed in groups but permit little contact between offspring & other group members, thereby, assuming high maternal costs, an apparent strategy whereby costs and benefits of group-living are minimized, as well as, maximized ... importantly, humans may be the only animal species in which all reproductive costs can, effectively, be eliminated by females [and males, also]... all phenotypic traits of vertebrate, here, mammal females should be evaluated in terms of their ability to minimize the costs of maternal care ... costs & benefits to young should, also, be evaluated and whether young can ever "win" in "fitness" conflicts with the mother ... Trivers (1972) was of the opinion that, in certain contexts, offspring can "win;" Alexander (1974) was skeptical ... the question can only be resolved by measuring the "fitness" costs of offspring's behavior toward mothers, & vice versa ...

3... Currently, the consensus is that Humans are not characterized by "reproductive division-of-labor;" thus, the consensus is that humans are not "eusocial" (cf. Crespi 2014) ... Human females [& human males] are unique in being able to relieve themselves of reproductive costs except for the production of eggs [ovulation (& ejaculation) can be avoided by culling of eggs (& sperm)] ... this remarkable capacity for reproductive flexibility contrasts with social insect Queens [females] who relieve themselves, obligately, from all tasks associated with reproduction except for insemination, egg production, & laying ... in Mammals, Eusociality may be viewed as a continuum whereby more or less exclusive [though, not, obligate] "Queens" [social mole rats; cooperative breeders] may perform most or all production of offspring and, also, perform other tasks or roles [e.g., feeding of young; defense] ... it is important to note that, given our knowledge to date, all mammalian [more or less non-reproducing] "helpers" are "totipotent," capable of breeding, & mammals exhibit a variety of mechanisms whereby reproduction is suppressed ... as David Macdonald has pointed out, Class Mammalia is characterized by phenotypic flexibility ... as an aside, solitary breeding, non-human great ape breeding mode, Cooperative Breeding, & Eusociality may be differentiated by breeders' relative degrees of task & role specialization [& investment] ...

4... Finally, recall that the evolution of groups* [from group formation to group maintenance], as well as, the evolution of/transition to sociality [Cooperation as per Hamilton op. cit., &, under some environmental conditions, the possible transition (evolution)  to Complex Sociality (specialization: division-of-labor--especially, Reproductive DoL; task, role, &/or morphological specialization)] is not inevitable or necessarily reproductively beneficial from the female's ["fitness"] perspective ... Interdependence, the precursor to the evolution of Cooperation is not inevitable, or, necessarily, beneficial, either ... the evolution of groups depends upon abiotic [e.g., climate] and biotic [especially, (clumped) food dispersion] environmental regimes, as well as, species-typical phenotypic traits ... the evolution of Complex Sociality is necessarily dependent upon the evolution of specialization which must first evolve at some point in the "grade," Cooperation ... in addition to environmental factors, the evolution of the female transition from the reproductive costs & benefits of breeding in a solitary state to breeding in a group depends, in part, upon evolved species-specific  traits of females [& offspring], as well as, environmental context, such as, dispersion of  breeding sites, and predation pressure] ... competition with other females from access to these and other limiting resources will, to a large degree, determine the relative reproductive costs & benefits of breeding in a solitary state to breeding in a group and, ultimately, female dispersion [distribution and abundance in Time & Space] ... a major factor determining whether or not it is reproductively beneficial for females to transition [evolve] from breeding in a solitary state to breeding in a group is her ability to narrow her niche [in particular, her feeding niche], becoming more specialized, in order to minimize competition for limiting resources, one of the major "fitness" costs of group life [see RD Alexander 1974; also, cf. reference cited below] ... in short, ceteris paribus, comparing the relative reproductive costs and benefits to a female from breeding in a solitary state to breeding in a group, either might be most beneficial depending upon initial conditions--species-typical female [& offspring] traits, as well as, environmental regime ... it is not necessarily beneficial for females to breed in groups or for sociality [Cooperation as per Hamilton op. cit.] & Complex Sociality, to, subsequently, evolve ... "decisions" about breeding in a solitary state vs. breeding in a group context depend upon differential costs & benefits to breeders' "fitness" ["relative reproductive success"] ...

*after group-formation, group-maintenance will not evolve unless limiting resources are "clumped" in T & S ... the evolution of group-maintenance is not necessarily beneficial to an organism's lifetime reproductive success ["fitness"] ... some Behavioral Ecologists have hypothesized that groups will not evolve in response to predation alone ...

References

Alexander RD (1974) The evolution of social behavior. Ann Rev Ecol Syst 5: 325-383.

Eisenberg JF (1981) The mammalian radiations: an analysis of trends in evolution. The University of Chicago Press, IL.

Hamilton WD (1964) The genetical evolution of social behavior. J Theor Biol 7: 1-52.

Hrdy SB (1976) Care and exploitation of non-human primate infants by conspecifics other than the mother. Adv Stud Behav 6: 101-158.

Jones CB (2020) Female mantled howler monkey (Alouatta palliata palliata: Primates, Atelidae) life-history strategies--a "major transitions approach" to mammalian social evolution. lulu dot com

Schoener TH (1971) Theory of feeding strategies. Ann Rev Ecol Syst 22: 369-404.

Sheppard CE, et al. (2018) Intragroup competition predicts individual foraging specialization in a group-living mammal. Ecology Letters 21: 665-673.

Trivers RL (1972) Parental investment and sexual selection. In B Campbell (ed) Sexual selection and The descent of man (1871-1971). Aldine, Chicago, pp 136-179.

West SA, et al. (2015) Major evolutionary transitions in individuality. PNAS 112(33): 10112-10119.

Wilson EO (1971) The insect societies. Belknap, Harvard, Cambridge, MA.

Wittenberger JF (1980) Group size and polygamy in social mammals. Am Nat 115: 197-222.

Clara B. Jones, October 2023, Silver Spring, MD, USA

Negative Impacts of the Social Sciences on Behavioral Ecology & Social Biology

 

Clara B. Jones

Email: foucault03@gmail.com; mapcbj@gmail.com

Twitter: @cbjones1943

Date: 8/28/2022

In many ways, the Social Sciences have a disproportionate & unfortunate influence on Behavioral Ecology, including, Social Biology, some of which follow [in no particular order]:

The Social Sciences Approach to Behavioral Ecology, including, Social Biology, and, Animal Behavior, in general, might be viewed as the Scala Naturae Approach since it centers Homo sapiens as the measure of and pinnacle of Social Evolution, especially, as derived from the purported complexity of human societies driven by higher-order cognitive traits, including, an obsession with "big brains." A fundamental principle of Complexity Theory is that complexity emerges from simple rules [after which it may be acted upon by Natural Selection, in the cases of evolved traits, see Duarte et al., 2011].

The Social Sciences Approach begins with the assumption that humans are complex [contrast with the Major Transitions Approach]. Instead of making the a priori assumption that humans are complex, practitioners of the Social Sciences approach should begin with the null hypothesis, Humans are not complex.

It is common for Anthropologists to suggest that human phenotypic diversity is too complex to figure out ["irreducible complexity" as per Stephen Wolfram] or that it has no adaptive value. One of a scientist's responsibilities is to search for patterns and to "unpack" variation. Social scientists have made no headway on this score. For example, the ideas in the field, "evolutionary cultural Anthropology" are tortuously complex [sic] & obfuscating. This field is an example of investigators of human behavior starting with the assumption that humans are complex, rather than beginning with the above null hypothesis, as well as, simple hypotheses & mechanisms.

The Social Sciences Approach [Scala Naturae Approach] is not based on 1st Principles [Physics; Ecology (acquisition; consumption; allocation)].

The Social Sciences do not define theory as mathematics, as the Sciences do. In the Social Sciences, theory is, generally, verbal, & many studies are purely descriptive Natural History, without quantitative treatment beyond Descriptive Statistics.

Social Science research is generally not hypothetico-deductive.

Social Science researchers, in Behavioral Ecology, including, Social Biology, are, generally, averse to field experiments, math modeling, & simulation modeling. It is rare to find studies in the previous fields using Individual- [Agent-] Based simulations to conduct experiments.

Social Science researchers have generally not studied Introductory Ecology & Population Ecology taught by specialists. Behavioral Ecologists, including, Social Biologists, are Autecologists & Population Ecologists. Social Scientists, in general, seem unaware of the literature in Ecology, Population Biology, & Social Biology [e.g., EO Wilson's 1971, The Insect Societies, arguably, the greatest book written to date in Animal Behavior]. Even JH Crook's 1964, classic weaver bird monograph, arguably, marking the inception of the field, Behavioral Ecology, seems unknown to the majority of Social Scientists.

Social Science researchers rarely link their work to [population-level] Evolutionary causes & outcomes. 

Social Science researchers are fond of Group Selection.

Social Science research rarely uses terminology consistently [e.g., "aggregation" is often used synonymous to "group"].

Terminology in Social Science research is not standardized. To be fair, terminology is not standardized or used consistently in Animal Behavior, generally, including, Behavioral Ecology & Social Biology. For an introductory discussion on "terminology" in the previous fields, see my YouTube video.

Most Social Scientists studying Behavioral Ecology, including, Social Biology, seem to misunderstand WD Hamilton's Rule, rb - c >0, by assuming that the formulation predicts that it is always in Actor's [reproductive] interest to benefit the reproduction of kin.

To my knowledge, where social evolutionary transitions are discussed by Social Scientists [including, Evolutionary Psychologists] at all, the Major Transitions Approach, a general model, has not influenced the Social Sciences, including, Anthropology. Readers are referred to my YouTube video, Mammal Social Evolution: A Major Transitions Approach, for an introduction, as well as, to the first blogpost of this blog.. In the MTA applied to social evolution, Cooperation is the gateway to Complex Sociality [Reproductive Division-of-Labor; Specialization]. In his 2019 book, Genesis, Wilson broadens the definition of "eusocial," limiting it to the character trait, Reproductive Division-of-Labor, & denotes Humans, as well as, some other Mammals as "eusocial." It is important to note that Wilson creates a series of 6 transitions from simple to complex sociality that differ in significant ways from the classical formulation. Wilson's [and, some others'] pinnacle stage of social complexity is "language," consistent with a social scientific, Scala Naturae Approach.

References

Crook JH (1964) The evolution of social organization and visual communication in the weaver birds (Ploceinae). Behaviour Supplement #10: 1-201.

Duarte ANA, Weissing FJ, Pen I, Keller L (2011) An evolutionary perspective on self-organizing division-of-labor in social insects. Ann Rev Ecol Syst 42: 91-110.

Wilson EO (1971) The insect societies. Belknap (Harvard), Cambridge, MA.

Wilson EO (2019) Genesis: the deep origins of societies. Liveright, NY.

General Schema For The Analysis Of Mammalian Inter-individual Interactions (Clara B. Jones)

 In Community Ecology, there are three (3) types of species-species interactions: Competition [-, -]; Predator-Prey [+, -]; Mutualism [+, +]. 

For studies in Population Ecology, we can interpolate these three types of interactions from the Community-level to the Population-level--interactions between individuals of the same species (inter-individual interactions*). Thus, the three (3) types of inter-individual interactions become: Competition [-, -]; Selfish or Social Parasitism [+, -]; Social [Cooperation (+, +), Altruism (-, +)]. This schema can, also, be employed to analyze inter-group interactions.

When quantified, these 3 types of inter-individual interactions can be employed to classify all interactions, effecting the decomposition of variability.

As for inter-specific interactions, inter-individual interactions may be Facultative or Obligate.

2020 self-published book: mammal social organization, female mantled howler monkey life history [PDF; order hardcopy] (Clara B. Jones)

 Citation [122 page book available in hard copy at Lulu "dot" com]

Jones CB (2020) Female mantled howler monkey (Alouatta palliata

palliata: Primates, Atelidae) life-history strategies—a “major transi-

tions” approach to mammalian social evolution. Lulu.com.

Abstract: Howler monkeys [Alouatta spp.] are wholly herbivorous. Based on earlier work by the present author [1978; 1980], the "age-reversed" dominance system is described whereby young adult mantled howler females are dominant to older females; middle-aged females are dominant to old females and are subordinate to young females; and, old females are subordinate to young and middle-aged females. The dominance system is characterized by "temporal division-of-labor" ["age polyethism"] whereby "social foraging" exhibits work [foraging, in the present case] graded by age, with old female "workers" ["helpers"] engaged in most foraging activities for variable plant resources, young females accounting for least. Adult female life-history parameters are described based on a "life table" and shown to correspond to patterns of temporal environmental cycles, in particular, the 6-month pattern of rainfall which females can "track" relative to "generation time." To my knowledge, this is the first demonstration of "temporal division-of-labor" in primates. Cooperatively-breeding primates/mammals exhibit, by definition "reproductive division-of-labor," the first stage of "complex sociality" in mammals. Reproductive division-of-labor is absent in mantled howler monkeys. Social mole-rats have been shown to exhibit both temporal and reproductive division of labor.

References

Jones CB (1978) Aspects of reproduction in the mantled howler monkey (Alouatta palliata Gray). Unpublished Ph.D. dissertation, Cornell University, Ithaca, NY.

Jones CB (1980) The functions of status in the mantled howler monkey (Alouatta palliata Gray): intraspecific competition for group membership in a folivorous Neotropical primate. Primates 21: 389-405.

Abstract: Predictors of male residence patterns in groups of black howler monkeys (Jones et al)

Jones CB, Milanov V, Hager R (2008) Predictors of male residence patterns in groups of black howler monkeys. Journal of Zoology 275: 72-78.

Abstract: Males may share access to fertilizable females (polygynandry) in one environment while, under other conditions, polygynous (one-male or "harem") mating is the norm [in mammals]. However, few studies in mammals have empirically investigated the factors predicting when males will oexist in bisexual reproductive units rather than live in one-male associations with females. We examined patterns of male group membership in a population of black howler monkeys, Alouatta pigra, residing in two habitats (deciduous and riparian of a tropical moist forest environment in Belize, Central America. Using general linear and logistic regression modeling, we evaluated nine variables as possible predictors of male residence patterns (one-male groups or multimale groups). Our results suggest that adult sex ratio and group size are the best predictors of male residence patterns in both habitats. Our findings provide empirical support for theoretical expectations that male reproductive strategies will be a function of habitat-related demographic patterns and the subsequently varying potential of males to monopolize females in heterogeneous regimes. This study may have important implications for our understanding of features of mammalian societies in which males compete directly for access to females.

Summary: An exploratory analysis of developmental plasticity... [CB Jones]

Jones CB (2005) An exploratory analysis of developmental plasticity in Costa Rican mantled howler monkeys (Alouatta palliata palliata Gray). In A. Estrada, PA Garber, MSM Pavelka, LeA Luecke (eds.), New perspectives in the study of Mesoamerican primates: distribution, ecology, behavior, and conservation. Springer, New York.

Summary: The topic of developmental plasticity is fundamentally related to life-history evolution (West-Eberhard 2003), in particular, patterns of survival and reproduction. Jones (1997b) employed matrix analysis (see Alberts & Altmann 2003) of Scott's census data with age structure for mantled howlers at Hacienda La Pacifica to estimate life-history parameters including survivorship, fecundity, and mortality. The suite of life-history traits described by this author (e.g., low survivorship in more than one age class, iteroparity, relatively small reproductive effort) is consistent with the view that mantled howlers, and, possibly other members of the genus, express tactics and strategies minimizing costs to fecundity. Since changes in CC [Chest Circumference] and/or CC:P [Chest Circumference : Pubis Width] are irreversible morphological changes, it is proposed that female mantled howlers are capable of responding to local conditions with mechanisms of developmental plasticity, a within-individual strategy compatible with the life-history strategy of mantled howlers (Meyers & Bull 2002; Table 1; see Ravosa et al. 1993). Further research is required to test alternate hypotheses for the present results (e.g., natural selection [C.P. Groves, pers. comm.; F. Nihout, pers. comm.]) and to examine the possibility that there is a threshold of response to locally stressful conditions in irrigation habitat exhibited by female howlers and manifested as developmental plasticity in CC and CC:P.

The present report is consistent with the program of Stearns et al. (2003: 311) expressed in the following statement: "Alternative explanations for characteristic male and female growth schedules, and the consequences of the patterns seen in each species...all call for investigation across the spectrum of primate social systems." The study of the functional ecology, including physiological ecology and developmental plasticity, of primates is in its early stages (Milton 1998; also see Strier 1992; Ravosa et al. 1993; Crockett 1998; Reader & Laland 2003: 20-21; Jones 2005), investigations which are likely to occupy laboratory and field investigators for many years. This body of research will have important implications on primate and other mammalian development, energetics, life history evolution, and conservation, as it involves an understanding of growth, survival, and reproduction relative to environmental regimes.

References

Alberts SC, Altmann J (2003) Matrix models for primate life history analysis. In PM Kappeler, ME Pereira (eds.), Primate life histories and socioecology. University of Chicago Press, pp 66-102.

Crockett CM (1998) Conservation biology of the genus Alouatta. Int. J. Primatol. 19: 549-578.

Jones CB (2005) Behavioral flexibility in primates: causes and consequences. Springer, New York.

Meyers LA, Bull JJ (2002) Fighting change with change: adaptive variation in an uncertain world. Trends Ecol Evol 17: 551-557.

Milton K (1998) Physiological ecology of howlers (Alouatta): energetic and digestic considerations and comparison with the Colobinae. Int J Primatol 19: 513-548.

Ravosa MJ, Meyers DM, Glander KE (1993) Relative growth of the limbs and trunk in sifakas: heterochronic, ecological, and functional considerations. Am J Phys Anthropol 92: 499-520.

Reader SM, Laland KN (2003) Animal innovation: an introduction. In SA Reader and KN Laland (eds.), Animal innovation, Oxford University Press, Oxford, pp 3-35.

Stearns SC, Pereira ME, Kappeler PM (2003) Primate life histories and future research. In PM Kappeler, ME Pereira (eds.), Primate life histories and socioecology. University of Chicago Press, pp 301-312.

Strier KB (1992) Ateline adaptations: behavioral strategies and ecological constraints. Am J Phys Anthropol 88: 515-524.

Abstract: Multi-modal communication by male mantled howler monkeys [Jones & Van Cantfort]

Jones CB, Van Cantfort TE (2007) Multimodal communication by male mantled howler monkeys ( Alouatta palliata palliata Gray) in sexual contexts: a descriptive analysis. Folia Primatol 78: 166-185.

Abstract: We analyzed continuously sampled focal and ad libitum data of male mantled howler Cmonkeys (Alouatta palliata palliata Gray) observed in random order. Males resided in two groups in a Costa Rican tropical dry forest environment (riparian habitat group: 3 adult males, 15 adult females, 402 h observation; deciduous habitat group: 2 adult males, 8 adult females, 114 h observation). Samples were limited to sexual contexts, in particular, the 60-min periods before and after each copulation observed within each group for each adult male. Time samples for each male were distributed equally before and after their own copulations. Before statistical analyses were conducted, data were corrected for differences in time sampled for males within each group. Four types of multimodal signaling were resolved: (1) audiovisual, (2) olfactory-visual, (3) olfactory-visual-tactile, and (4) tactile-gustatory. Olfactory and tactile signals were never observed in combination with auditory signals. Consistent with expectation for a Neotropical, arboreal species, audiovisual signals were the most frequently observed type of multimodal communication in both groups (riparian habitat group: n= 139; deciduous habitat group: n= 66). Our evidence strongly suggests that unimodal signals may be combined and recombined to form complex, multimodal signals. Subordinate males in each group were more likely than dominant males to emit audiovisual signals before their own copulations. Male dyads were compared to assess the relative rate of audiovisual signaling by one male before another male's copulations. On average, the subordinate male of the riparian habitat group exhibited audiovisual signals at a higher rate before his own copulations compared to the rate of audiovisual signaling by his dominant challengers. The same comparisons are not significant for males in the deciduous habitat group. The pattern of male response that we report whereby subordinates emit some complex signals at a higher rate than dominants supports the "terminal investment hypothesis" predicting that organisms should increase reproductive effort with age since, in mantled howlers, age correlates negatively with dominance rank. Additional, qualitative observations suggested that subordinates in both groups were most likely to obtain copulations when they increased rates of complex signaling and/or escalated interactions with their male challengers. Group differences were apparent, however, and we suggest factors that may account for these patterns. We assessed responses by female receivers of complex signals emitted by males in sexual contexts. In general, higher-ranking males are more attractive to females and are more successful at monopolizing them. Findings for other, less frequently displayed, multimodal signals (olfactory-visual, olfactory-visual-tactile, and tactile-gustatory) are presented and discussed. We conclude with the suggestion that howlers may be a robust model for the investigation of complex signals in Neotropical primates, including research on functionally referential communication and context-dependent syntax.