Mammoth Energy Services, Inc.
DE ˙ DB ˙ US56155L1089
2,78 € ↑0,10 (3,73%)
2026-06-01
DEL PRIS
SecurityDE:5M8 / Mammoth Energy Services, Inc.
InstitutionBoston Partners
Latest Disclosed Ownership154,388 shares
Latest Disclosed Value $ 378,250
Boston Partners ownership in 5M8 / Mammoth Energy Services, Inc.

On May 11, 2026 - Boston Partners filed a 13F-HR form disclosing ownership of 154,388 shares of Mammoth Energy Services, Inc. (DE:5M8) valued at $339,654 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 7, 2024 disclosing 0 shares of Mammoth Energy Services, Inc.. The current value of the position is $429,199 USD.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date		 Effective
Date		Form Security Class ID Avg Price
Paid (Est)		 Reported
Shares		 ΔShares ΔShares
(%)		 Reported
Value
(x1000)		 ΔValue
(%)		 Alloc
(%)		 ΔAlloc ΔAlloc (%) Cost Basis
(x1000)		 Unrealized
Gain/Loss
(x1000)
2026-05-11 2026-03-31 13F MAMMOTH ENERGY SVCS COM 56155L108 154,388 154,388 378 0.0002
2024-02-07 2023-12-31 13F MAMMOTH ENERGY SVCS COM 56155L108 0 -35,093 -100.00 0 -100.00
2023-11-08 2023-09-30 13F MAMMOTH ENERGY SVCS COM 56155L108 35,093 -27,093 -43.57 163 -46.00 0.0002
2023-08-10 2023-06-30 13F MAMMOTH ENERGY SVCS COM 56155L108 62,186 21,758 53.82 300 76.47 0.0004
2023-05-09 2023-03-31 13F MAMMOTH ENERGY SVCS COM 56155L108 40,428 -4,645 -10.31 171 -56.30 0.0002
2023-02-08 2022-12-31 13F MAMMOTH ENERGY SVCS COM 56155L108 45,073 0 0.00 390 152.60 0.0005
2022-11-09 2022-09-30 13F MAMMOTH ENERGY SVCS COM 56155L108 45,073 -27,079 -37.53 154 -3.14 0.0002
2022-08-10 2022-06-30 13F MAMMOTH ENERGY SVCS COM 56155L108 72,152 -70,110 -49.28 159 -47.52 0.0002
2022-05-10 2022-03-31 13F MAMMOTH ENERGY SVCS COM 56155L108 142,262 79,561 126.89 303 165.79 0.0004
2022-02-04 2021-12-31 13F MAMMOTH ENERGY SVCS COM 56155L108 62,701 -13,677 -17.91 114 -48.65 0.0001
2021-11-05 2021-09-30 13F MAMMOTH ENERGY SVCS COM 56155L108 76,378 28,653 60.04 222 1.37 0.0003
2021-08-12 2021-06-30 13F MAMMOTH ENERGY SVCS COM 56155L108 47,725 -204,290 -81.06 219 -60.54 0.0003
2020-02-06 2019-12-31 13F/A-1 MAMMOTH ENERGY SVCS COM 56155L108 252,015 -127,467 -33.59 555 -41.02 0.0007
2020-02-05 2019-12-31 13F MAMMOTH ENERGY SVCS COM 56155L108 252,015 -127,467 555 312.0372
2019-11-20 2019-09-30 13F/A-1 MAMMOTH ENERGY SVCS COM 56155L108 379,482 -580,225 -60.46 941 -85.75 0.0013
2019-11-08 2019-09-30 13F MAMMOTH ENERGY SVCS COM 56155L108 959,707 0 6,603 0.0087
2019-08-26 2019-06-30 13F/A-1 MAMMOTH ENERGY SVCS COM 56155L108 959,707 495,089 106.56 6,603 -14.65 0.0087
2019-08-09 2019-06-30 13F MAMMOTH ENERGY SVCS COM 56155L108 959,707 495,089 6,603
2019-05-13 2019-03-31 13F/A-1 MAMMOTH ENERGY SVCS COM 56155L108 464,618 -436,202 -48.42 7,736 -52.24 0.0102
2019-05-03 2019-03-31 13F MAMMOTH ENERGY SVCS COM 56155L108 464,618 -436,202 7,736
2019-02-07 2018-12-31 13F MAMMOTH ENERGY SVCS COM 56155L108 900,820 649,972 259.11 16,197 121.88 0.0233
2018-11-14 2018-09-30 13F MAMMOTH ENERGY SVCS COM 56155L108 250,848 99,783 66.05 7,300 42.30 0.0085
2018-08-03 2018-06-30 13F MAMMOTH ENERGY SVCS COM 56155L108 151,065 66,965 79.63 5,130 90.28 0.0061
2018-05-04 2018-03-31 13F MAMMOTH ENERGY SVCS COM 56155L108 84,100 -66,940 -44.32 2,696 -9.07 0.0033
2018-02-14 2017-12-31 13F/A-1 MAMMOTH ENERGY SVCS COM 56155L108 151,040 2,771 1.87 2,965 18.60 0.0035
2018-02-01 2017-12-31 13F MAMMOTH ENERGY SVCS COM 56155L108 151,040 2,771 2,965
2017-11-02 2017-09-30 13F MAMMOTH ENERGY SVCS COM 56155L108 148,269 99,340 203.03 2,500 174.73 0.0031
2017-08-02 2017-06-30 13F MAMMOTH ENERGY SVCS COM 56155L108 48,929 -7,071 -12.63 910 -24.48 0.0012
2017-05-03 2017-03-31 13F MAMMOTH ENERGY SVCS COM 56155L108 56,000 8,400 17.65 1,205 66.44 0.0015
2017-02-06 2016-12-31 13F MAMMOTH ENERGY SVCS COM 56155L108 47,600 47,600 724 0.0010
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.