The nutritional composition of milk during primary and prolonged supplemental lactation in wild toque macaques (Macaca sinica)
Data files
Mar 20, 2026 version files 61.98 KB
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File_1._Field_record_for_milk_collections.csv
11.85 KB
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File_2._Milk_constituents_primary_and_supplementary_lactation.csv
24.50 KB
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File_3.Testing_milk_quality_vs_sampling_sequence_of_same_nipple.csv
2.44 KB
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File_4._Gross_energy_calulated_vs_bomb_calorimetry.csv
2.24 KB
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File_5._Research_participants_and_roles_1968-1994.csv
3.61 KB
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README.md
10.83 KB
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Variables_Definitions_File_1__Field_record_for_milk_collections.csv
2.88 KB
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Variables_Definitions_File_2._Milk_constituents_primary_and_supplementary_lactation.csv
2.64 KB
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Variables_Definitions_File_3._Testing_milk_quality_by_nipple_sequence.csv
983 B
Mar 24, 2026 version files 62.28 KB
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File_1._Field_record_for_milk_collections.csv
11.85 KB
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File_2._Milk_constituents_primary_and_supplementary_lactation.csv
24.52 KB
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File_3.Testing_milk_quality_vs_sampling_sequence_of_same_nipple.csv
2.44 KB
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File_4._Gross_energy_calulated_vs_bomb_calorimetry.csv
2.24 KB
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File_5._Research_participants_and_roles_1968-1994.csv
3.76 KB
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README.md
10.89 KB
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Variables_Definitions_File_1__Field_record_for_milk_collections.csv
2.92 KB
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Variables_Definitions_File_2._Milk_constituents_primary_and_supplementary_lactation.csv
2.66 KB
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Variables_Definitions_File_3._Testing_milk_quality_by_nipple_sequence.csv
1 KB
Abstract
This study complements a recent revelation that wild toque macaques (Macaca sinica) and other cercopithecine primates in natural environments may prolong lactation up to 24 months compared to well-fed monkeys under food provisioned conditions that normally cease lactation by about 7 months postpartum (Dittus and Baker, 2023). We analyzed changes in the composition of milk from 72 wild toque macaques to assess its nutritional role both during primary lactation (< 7mo), when infants were highly dependent upon milk for nutrition, and subsequently when infants fed mainly from the environment but supplemented their diet with milk (7 mo to >18 mo). In our study, female toque macaques were briefly captured, sedated, and released (within one day) during 5 different years in the period 1986 to 1994 at the natural forest site at Polonnaruwa Sri Lanka, where long-term socio-ecological research has been conducted (1968-2024). All macaques were individually identified and had known life histories. Five data sets are presented: (i) the demographic variables and individual identities of the mother-infant dyads, and the field collection details of milk sampling. (ii) An analysis of 19 different constituent variables of milk (water, fat, protein, sugar, gross energy, minerals and electrolytes), their prevalence in relation to all infant ages, a comparison of their prevalence between (a) primary lactation (< 7mo) and supplementary lactation (7 – 26 mo) in wild toque macaques and (b) with primary lactation in other cercopithecines from food rich breeding colonies among which supplementary lactation has not been observed. For toque macaques, methodological verifications were done concerning (iii) compositional changes in milk with sequential nipple stripping, and (iv) calculated gross energy content of milk with bomb-calorimetry. (v) A final data set indicates the names of participants who contributed to the long-term demographic records, milk collections, and laboratory analyses of milk composition.
https://doi.org/10.5061/dryad.dz08kps67
Description of the data and file structure
GENERAL INFORMATION
Title of Dataset: The nutritional composition of milk during primary and prolonged supplemental lactation in wild toque macaques (Macaca sinica)
In support of publication:
Dittus, WPJ, Childs-Sanford SE, Jayawickrama LH, Oftedal OT (2025). Is extended lactation nutritionally important for the weaning of wild toque macaques (Macaca sinica)? Evidence from milk composition. American Journal of Primatology 87(9): e70078. DOI 10.1002/ajp.70078
Author/Principal Investigator Information
Name: Wolfgang P J Dittus (WD)
ORCID: 0000-0001-7981-3968
Institution: Smithsonian Institution USA, \& National Institute of Fundamental Studies, Sri Lanka
Address: Washington, DC,20008
Email: wdittus@gmail.com; DittusW@SI.edu; Wolfgang.di@nifs.ac.lk
Author/Co-investigator Information
Name: Olav T. Oftedal (OTO)
ORCID: n/a
Institution: Conservation Ecology Center, Nutrition Laboratory, National Zoological Park
Address: Washington, DC 20008
Email: otoftedal@gmail.com
Author/Co-investigator
Name: Lalith Jayawickrama (LJ)
ORCID: n/a
Institution: Conservation Ecology Center, Nutrition laboratory, National Zoological Park
Address: Washington, DC 20008
Email: lalithj@dbq.edu
Author/Co-investigator
Name: Sara E. Childs-Sanford
Institution: Cornell University College of Veterinary Medicine
Ithaca, NY 14853-6401
Date of data collection:
Demography (vital statistics), 1968/10/15 to 2002/10/15. (WD)
Milk sampling: 1986/09/20 to 1994/08/26 (WD)
Geographic location for field observation of macaque vital statistics & milk sample collection: (WD)
Polonnaruwa Archaeological Reserve and Nature Sanctuary (study area)
Latitude/longitude: 7.991474 / 8099579
Town: Polonnaruwa, North Central Province, Sri Lanka
Smithsonian Primate Research Station (shown on Google map for Sri Lanka)
Information about funding sources that supported the collection of data (1968-1994)
Data relevant to this research were two in kind:
(1) Long-term (1968-1995) vital statistics for individually identified wild toque macaques. Data were integral to varied objectives supported by many grants 1968 - 1994 as listed below.
Smithsonian Institution: 1968-1972 (PI: John Eisenberg) NSF GB-3545
Smithsonian Foreign Currency: 1968-1972 (PI: John Eisenberg) #SFC-7004
National Geographic Society: 1975-1986 (Wolfgang Dittus, WD) #1442
US National Science Foundation (NSF) 1976-1996 (WD #BNS-7619740, -7924057, -9300092, -9104649)
US National Science Foundation (BSF): 1986-1989 joint grant (Don Melnick and WD) #BNS-8608187, -8909775
Wenner-Gren Foundation for Anthropological Research: 1980 (WD) #3199
Harry Frank Guggenheim Foundation: 2 grants 1986-1992 (WD)
Smithsonian Institution Scholarly Studies: (WD) 3 grants, 1986-1998
Smithsonian Institution, Sisley & Abbott Funds, 2 grants 1999-2003 (WD)
Earthwatch: 7 grants, 1992-2007 (WD)
Deutsche Forschungsgemeinschaft, 1976-1978 (WD) #Di73/1
(2) The laboratory analyses of the nutritional (biochemical) composition of toque macaque milk at the Nutrition Laboratory, Smithsonian National Zoo, was supported by:
Friends of the National Zoo (1989 - 1994), grant to Olav T. Oftedal
SHARING/ACCESS INFORMATION
License/restrictions placed on the data: n/a
Links to publication that have used the some of the data:
- Dittus W, Baker A. (2023). Maternal care in wild toque macaques (Macaca sinica) involves prolonged lactation and interbirth intervals as adaptations to reduce maternal depletion and infant mortality in harsh environments. American Journal of Primatology 2023:e23584. doi:10.1002/ajp.23584
- Goto K, Fukuda K, Senda A, Saito T, Kimura K, Glander K, Hinde K, Dittus W, Milligan L, Power M, Oftedal O, Urashima T. (2010). Chemical characterization of oligosaccharides in the milk of six species of New and Old world monkeys. Glycoconjugate Journal, 27, 703-715. doi:10.1007/s10719-010-9315-0
- Milligan L, Rapoport S, Cranfield M, Dittus W, Glander K, Oftedal O, Bazinet R (2008). Fatty acid composition of wild anthropoid primate milks. Comparative Biochemistry and Physiology, Part B., 149, 74-82. doi:10.1016/j.cbpb.2007.08.006
Links to other publicly accessible locations of the data: to be determined
Links/relationships to ancillary data sets: Dittus, Wolfgang (2023). The biology of prolonged lactation in wild Macaca sinica: interbirth intervals, maternal depletions, infant mortality [Dataset]. Dryad. https://doi.org/10.5061/dryad.cc2fqz695
Was some data derived from another source: n/a
DATA & FILE OVERVIEW
Files and variables
File#1: Field_record_for_milk_collections.csv
Description: This documents the data collected at the field study site at Polonnaruwa, Sri Lanka, by WD, concerning the life history variables for the toque macaque individuals (mother-offspring dyads) that were involved in the collection of milk samples between 1986 and 1994. It also includes the details of the collected milk samples. The file has two related spreadsheets in CSV format:
(i) "File#1 Field record for milk collections.csv" and
(ii) "Variables Definitions File#1, Field record for milk collections.csv"
Variables:
- Variables are two in kind: (1) vital statistics for the mother-infant pair that contributed to the milk sample, including individual monkey identities, age, sex, social group affiliation, processing date; and (2) details about processing times, duration since infant last nursed before milk sample collection, number and sequence of vials of milk collected and the body position of the nipple sampled.
- Altogether, 23 variables are listed and defined. Not all listed variables, however, were used in the analysis of milk constituents and the resulting publication.
File#2: Milk_constituents_in_primary_and_supplementary_lactation.csv
Description: The sources for this information are the records at the Nutrition Laboratory, National Zoo, and concern the results of the analyses of milk samples (n=72) that were collected in Sri Lanka (File #1). The file details the analytical results of major milk constituents: water, fat, protein sugar, their energy values, as well as the minerals; Calcium (Ca), Phosphorous (P), Zinc (Zn), Magnesium (Mg), and the electrolytes; Sodium (Na), Chloride (Cl), and Potassium (K). Measures of these constituents were related to macaque infant age and the phase of lactation in primary and supplemental lactation. The file has two related CSV worksheets:
- (i) File#2. Milk constituents in primary and supplementary lactation.csv, and
- (ii) Variables Definitions File#2. Milk constituents in primary and supplementary lactation.csv
Variables
- Each milk constituent analyzed is linked to the identity of the mother and the known age of the nursing infant.
- Altogether 29 variables were used in analyses and they are defined in the 2nd CSV file. In the target publication for these results, variables are marked according to the number of the table and/or figure where the variables are used in the analyses.
File#3: Testing_milk_quality_vs_sampling_sequence_of_same_nipple.csv
Description: In the field, six milk samples were collected from either the right or left nipple of five different lactating females. The analyses measure the change in constituent values in relation to the sequence in which milk samples were nipple stripped during collection from either the right or left nipple of the focal female. The analytical results are shown in the first CSV worksheet:
- (i) File#3. Testing milk quality vs sampling sequence of same nipple.csv.
- (ii) Variables Definitions File#3, Testing milk quality by nipple sequence.csv"
Variables
- The variables identifying the mother and infant dyad, milk sampling sequence by right or left nipple, and analytical results for Dry Matter, Fat, Protein, Sugar, Total, and Gross Energy are displayed in the first worksheet and the variables are defined in the Variables Definitions File#3.
File#4: Gross_energy_calulated_vs_bomb_calorimetry.csv
Description: The data show a comparison between the gross energy (GE calc) as computed from the % wet weight composition of milk constituents: Dry matter (DM), Fat, Protein, Sugar and Total and that established by bomb calorimetric methods. Calculated gross energy follows the formula in Oftedal (1984): GE (kcal/g) = (9.11Fat%+5.86protein%+3.95*sugar%)/100. Bomb calorimetric analyses follow Oftedal et al. (2014) and Hood et al. (2009).
Variables
- The variables are defined in "Variables Definitions File#2. Milk constituents in primary and supplemental lactation.
File#5: Research_participants_and_roles.csv
Description: Research participants were two in kind: Firstly, personnel at the field site in Sri Lanka who were involved in the long-term observations (1968-1995) to establish the identity of focal macaque individuals, their ages and genealogies. Some field personnel were also involved in the collection of milk samples. Secondly, technical personnel in the Nutrition Laboratory, National Zoo, who assisted with the legal permits, transport, storage, and analyses of the biochemical composition of milk samples.
Variables
- Research participants are listed by name, period of participation, role, and institutional affiliation. Roles are defined as: 1= clerical field data collation and record keeping in Sri Lanka and the USA; 2= field research concerning macaque individual identities, regular census, and demographic fates (birth, death, emigration, immigration, growth, group transfer); 3= capture of macaque subjects, individual-specific measurement of variables of interest, collection of milk samples; 4= field laboratory processing and/or veterinary monitoring; 5= laboratory biochemical analyses of milk composition at the National Zoo, USA.
Code/software
Microsoft 365 EXCEL for spreadsheet entries and CSV tabular format (Microsoft Corporation)
SigmaPlot 14.5 for statistical analyses and graphic figures (SYSTAT Software Inc)
Ethics: The methods of field observation, capture and release of macaques and milk sampling comply with all regulations regarding the ethical treatment of research subjects as prescribed by the National Institute of Fundamental Studies, Sri Lanka, and the Smithsonian's National Zoo and Conservation Biology Institute, USA, and adhered to the American Society of Primatologists principles for the ethical treatment of primates.
Individual animal identification: The methods involve hand-written notes and drawings of field observations of individually identified macaques in their natural habitat at Polonnaruwa, Sri Lanka, according to established protocols as described in earlier publications: National Research Council (1981), Techniques for aging and sexing primates. In: Techniques for the Study of Primate Population Ecology. pp 81-134, Washington, DC, National Academy Press. Also, Dittus WPJ (1990). Manual for the Identification of Individual Toque Macaques, Training manual, Smithsonian Primate Biology Program. All field research staff were trained in these methods.
Vital statistics: All macaques were individually identified and their dates of birth and death, age, sex, and reproductive condition were known from census logs. Individuals in all groups were subject to regular census about once per month. During the birth season females were checked once per week or more to pin-point dates of birth of infants. Such data were the basis for monitoring individual life-histories from birth to death (Dittus 2004). The chronological ages of nearly all individuals in this sample were based on known birthdates; those of a few individuals, that were born prior to 1968, were estimated from morphological development; females are physically mature or “adult” by 6 years old, and males by about 9 years old [Cheverud et al., 1992].
Capture and release. Procedures for the capture and release of macaques had been described earlier (Hoelzer et al., 1994). Macaques were habituated to enter steel mesh box traps (ca. 1×1×1.5m) which were baited with food for several days before the capture date. Upon capture, mothers and their young were separated, and the mothers were tranquilized with a single dose of IM injection of ketamine hydrochloride (Ketalar, Park Davis Co.). The dose tranquilized a mother for less than 40 min and in pregnant mothers was far below the threshold for toxicity in the mother or in fetal development (Paule et al., 2011; Zou et al., 2009). Notwithstanding, as a precaution, a few females were not sampled if they appeared in the late stage of pregnancy as evident from a well swollen abdomen.
Milk sampling, transport and storage. Sterile gloved hands were used for all procedures. Prior to milk collection, hair in the vicinity of each nipple was removed by shaving, and the nipple area cleaned with distilled water and dried. Females were injected IM with 0.20 cc (4 IU) oxytocin to induce milk let down. Milk was obtained by manual expression into 1.8 ml cryovials (1-10 cryovials per female, i.e., about 1.5-16 ml); an effort was made to evacuate the mammary glands as fully as possible. Immediately after collection milk sampled were submerged in liquid nitrogen for storage and transport from Sri Lanka to Washington, DC, USA. Milk was kept frozen at -20°C or colder throughout storage at the Nutrition Laboratory of the Smithsonian’s National Zoo and Conservation Biology Institute.
Milk sample analyses.
Milk samples were analyzed in this study from the 72 captured wild females whose infants ranged in age from 0.04 - 2.20 y. Of these capture events, 3 were repeat captures of the same mother but with different infants in separate lactation cycles. We examined changes in the composition of milk to assess its nutritional role both during primary lactation (<7 mo) and subsequent infant care up to 22 mo. Milk samples were assayed by standard methods and included the following variables that were related to changes in infant ages. The constituents of milk included water and dry matter comprising: fat, crude protein and sugar as well as the minerals calcium (Ca), phosphorus (P), magnesium (Mg), sodium (Na), potassium (K), chlorine (Cl), and zinc (Zn). Estimates were made of the proportional contribution to total gross energy per gram of milk from fat, protein and sugar. The molar weights of Na, K and Cl, and ppm for Zn as well as the ratio Ca:P were estimated. The above variables were compared with regression analyses to the two phases of lactation in toque macaques, as well as the primary phase (< 7mo) in other cercopithecine primates.
Integration of data sets: Information from different data logs were entered into EXCEL spreadsheets for the analysis of relationships among different variables. Variables were two in kind: firstly, demographic field identification of individuals, mother infant dyads, and infant age, notes relevant to milk sampling and lactation (See README file #1 for details); secondly, the results of biochemical or nutritional analyses for the different components comprising milk composition (See README files #2-4).
Definitions: All dataset files and variables were defined in the README files.
Changes after Mar 20, 2026:
24 March 2026. Data files #1, #2, #5, plus 3 variables definitions files and the README.md file were updated having been corrected for simple spelling errors in the original that had been created 19 March 2026, uploaded, and published.